LIBRARY 


UNIVERSITY  OF  CALIFORNIA. 


Class 


WORKS   OF   PROFESSOR   GOSS 

PUBLISHED   BY 

JOHN  WILEY  &  SONS. 


Locomotive  Performance. 

The  Results  of  a  Series  of  Researches  Conducted 
by  the  Engineering  Laboratory  of  Purdue  Uni- 
versity. 8vo,  xvi-J-  439  pages,  229  figures.  Cloth, 

$5.00. 

Locomotive  Sparks. 

8vo,  vii-f-  172  pages,  69  figures.     Cloth,  $2.00. 


LOCOMOTIVE  PERFORMANCE 


THE  RESULT  OF  A  SERIES  OF  RESEARCHES  CON- 
DUCTED BY  THE  ENGINEERING  LABORATORY 
OF    PURDUE    UNIVERSITY 


BY 


WILLIAM  F.  M.   GOSS,  M.S.,  D.E. 

Director  of  the  Engineering  Laboratory  arid  Dean  of  the  Schools  of  Engineering 
Purdue  University 


FIRST    EDITION 
FIRST   THOUSAND 


or  THF 
UNIVERSITY  J 

^.-.-' 


NEW    YORK 

JOHN  WILEY  &   SONS 
LONDON:   CHAPMAN   &   HALL,    LIMITED 

1907 


Copyright,  1906, 

BY 

WILLIAM  F.  M.  GOSS 


ROBERT  DRTTMMOND,  PRINTER,  NKW  YORK 


PREFACE. 


FOR  a  number  of  years  the  Engineering  Laboratory  of  Purdue 
University  has  concerned  itself  with  problems  relating  to  the 
performance  of  locomotives,  and  the  results  of  its  researches  have 
from  time  to  time  appeared  in  the  proceedings  of  various  scientific 
and  technical  societies.  This  process  of  publication  has  extended 
over  a  period  of  fourteen  years,  and  has  run  through  many  different 
channels,  with  the  result  that  the  record  now  exists  in  widely  scat- 
tered parts,  which  are  often  difficult  of  access  and,  therefore,  of  lim- 
ited usefulness. 

The  purpose  of  this  volume  is  to  combine  the  most  important 
of  these  results  with  other  material  not  before  published,  and  thus 
make  a  permanent  and  accessible  record  of  the  work  of  the  labora- 
tory. If  it  should  appear  that  the  pages  have  been  burdened  with 
too  great  an  array  of  detail,  it  should  be  rememhered  that  many 
prefer  such  a  minute  presentation  of  facts  as  will  enable  them  to 
work  out  conclusions  for  themselves.  Primarily,  the  volume  is  de- 
signed as  a  record  rather  than  a  text,  though  it  is  hoped  that 
it  will  prove  of  interest  and  value  to  any  who  wish  to  increase  their 
acquaintance  with  the  action  of  steam  locomotives. 

As  a  whole,  the  researches  are  the  outcome  of  many  influences. 
The  trustees  and  president  of  the  University  have  supplied  means, 
professors  and  instructors  have  assisted  in  working  out  the  problems- 
of  the  laboratory,  students  have  given  their  aid  as  observers,  and 
in  addition  to  these,  skilled  assistants  have  had  a  part  in  checking 
and  arranging  data. 

Much  work  and  many  plans  necessarily  preceded  the  actual  work 
of  the  laboratory,  and  whatever  may  have  been  accomplished  in  the 
development 'of  a  system  for  testing  locomotives  is  due,  in  the  first 
instance,  to  the  part  which  was  taken  by  the  late  President  Smart. 
It  required  some  courage  for  the  president  of  a  university  not 
rich  in  funds  to  respond  to  the  suggestion  of  a  department,  and, 

iii 


156495 


IV  PREFACE. 

in  the  absence  of  favorable  advice,  and  even  in  the  face  of 
some  adverse  criticism,  to  give  his  approval  and  support  to  an 
untried  process  involving  the  expenditure  of  a  considerable 
amount  of  money;  but  President  Smart  carefully  considered  every 
favorable  plea  and  weighed  every  objection,  and  when  he  finally 
decided  to  enter  upon  a  line  of  work  so  novel  as  that  of  testing  loco- 
motives in  a  laboratory,  he  took  a  bold  but  nevertheless  a  well-con- 
sidered and  intelligent  step.  He  afterward  imparted  so  much  of  his 
spirit  of  enthusiasm  to  the  Board  of  Trustees  as  led  them  out  of  the 
limited  resources  at  their  disposal  to  supply  means  for  executing  his 
plan;  and  later  still,  when  difficulties  appeared  in  the  development 
of  mechanical  matters,  he  was  ever  patient  with  delays,  helpful  in 
advice,  and  unfailing  in  his  support. 

Another  whose  help  counted  for  much  was  the  late  A.  J.  Pitkin 
while  General  Superintendent  of  the  Schenectady  Locomotive  Works. 
In  order  to  make  the  undertaking  a  success,  it  was  necessary  that 
funds  at  the  disposal  of  the  University  should  be  supplemented  by 
outside  aid,  and  it  was  through  the  friendly  influence  of  Mr.  Pitkin 
that  arrangements  were  finally  made  by  which  the  Schenectady 
Locomotive  Works  agreed  to  supply  a  suitable  locomotive  in  return 
for  the  small  sum  which  was  available.  Without  this  cooperation 
the  establishment  of  the  testing-plant  would  have  been  greatly 
delayed,  or  it  would  have  proceeded  under  conditions  far  less  favor- 
able than  those  which  afterward  existed.  Among  others  who 
early  lent  encouragement  to  the  work  of  the  testing-plant  should  be 
mentioned  Professor  James  E.  Denton,  Mr.  William  Forsyth,  and 
the  late  Mr.  David  L.  Barnes.  These  mechanical  engineers  were 
among  the  first  visitors  who  came  to  inspect  the  initial  testing- 
plant,  and  their  subsequent  interest  and  frequent  commendations 
went  far  to  gain  for  the  laboratory  a  degree  of  recognition  which, 
in  many  incidental  ways,  has  ever  since  been  helpful.  It  is  impos- 
sible to  acknowledge  properly  the  assistance  of  every  one  concerned 
in  the  actual  operation  of  the  laboratory,  but  mention  should  be 
made  of  Mr.  Richard  A.  Smart,  who  for  a  considerable  time  was  in 
immediate  charge  of  the  testing-plant,  and  of  Messrs.  Daniel  Royse 
and  Robert  S.  Miller,  who  each  for  a  period  of  one  year  checked 
the  numerical  work  of  students. 

W.  F.  M.  G. 

PURDUE  UNIVERSITY, 

LAFAYETTE,  INDIANA,  March,  1906. 


CONTENTS. 


I.   LOCOMOTIVE   TESTING. 

CHAPTER  I. 

THE  DEVELOPMENT   OF   THE   PURDUE   TESTING   PLANT. 

PAGE 

1.  The  Growth  of  Engineering  Laboratories  at  Purdue;  2.  Considerations  Lead- 
ing to  a  Locomotive  Testing  Plant;  3.  Arrival  of  the  Locomotive;  4.  The 
First  Testing  Plant;  5,  The  Supporting  Axles;  6.  The  Alden  Friction  Brakes; 
7.  Traction  Dynamometer;  8.  Behavior  of  the  Mounting  Mechanism  of  the 
First  Plant;  9.  The  Work  of  the  First  Plant;  10.  The  Second  Testing  Plant; 
11.  The  New  Wheel  Foundations;  12.  The  Emery  Dynamometer;  13.  The 
Superstructure;  14.  The  Building;  15.  Work  with  the  New  Plant;  16. 
Sale  of  Locomotive  Schenectady;  17.  Schenectady  No.  2 1 

CHAPTER  II. 

GROWTH   OF   INTEREST   IN    LABORATORY   TESTS    OF   LOCOMOTIVES. 

18.  Locomotive  Operation  under  Conditions  Other  than  Those  of  the  Track;  19. 
Growth  of  Interest  in  Locomotive  Testing;  20.  Interest  in  Purdue's  Work; 
2L  New  Plants 42 

CHAPTER  III. 

LOCOMOTIVE    SCHENECTADY   NO.    1. 

22.  Controlling  Conditions  Affecting  the  Choice  of  a  Locomotive;  23.  Specifi- 
cations; 24.  Drawings;  25.  Constants;  26.  Steam  Passages 46 

CHAPTER  IV. 

METHOD   OF  TESTING   AND  DATA. 

27.   Method  of  Testing;  28.  Data.. . , 69 

v 


vi  CONTENTS. 


II.   LOCOMOTIVE   PERFORMANCE:  A  TYPICAL  EXHIBIT. 

CHAPTER  V. 

LOCOMOTIVE  PERFORMANCE  AS  AFFECTED  BY  CHANGES  IN  SPEED  AND  CUT-OFF. 

PAGE 

29.  Purpose;  30.  The  Tests;  31.  The  Valves  and  Their  Setting;  32.  Indicator 
Cards;  33.  Events  of  the  Stroke;  34.  Wire-drawing;  35.  Mean  Effective 
Pressure;  36.  The  Indicated  Horse-power;  37.  The  Steam  Consumption; 
38.  Critical  Speed;  39.  Cylinder  Condensation;  40.  Boiler  Performance; 
41.  Performance  of  the  Locomotive  as  a  Whole;  42.  Maximum  Power  De- 
pendent upon  Efficiency 102 

III.   THE   BOILER. 

CHAPTER  VI. 

BOILER   PERFORMANCE. 

43.  Selection  of  Data;  44.  The  Boiler;  45.  General  Conditions;  46.  Actual 
Evaporation;  47.  Quality  of  Steam  and  Equivalent  Evaporation;  48. 
Power  of  Boiler;  49.  Coal  and  Combustible;  50.  Thermal  Units;  51.  Draft, 
Rate  of  Combustion,  and  Smoke-box  Temperature;  52.  Evaporative  Per- 
formance;  53.  Power  and  Efficiency;  54.  Efficiency  as  Affected  by  the 
Quality  of  Fuel;  55.  Derived  Relations;  56.  Conclusions 124 

CHAPTER  VII. 

HIGH   RATES    OF   COMBUSTION   AND    BOILER   EFFICIENCY. 

57.  General  Statement;  58.  The  Tests  and  the  Results;  59.  Grate  Losses;  60. 
Spark  Losses  as  a  Factor  Affecting  Grate  Losses;  61.  Losses  Due  to  Incom- 
plete Combustion  and  Excess  Air;  62.  Losses  along  the  Heating  Surface; 
63.  Conclusions.  .  .156 


CHAPTER  VIII. 

THE    EFFECT    OF   THICK   FIRING    ON    BOILER   PERFORMANCE. 

64.    The  Conception  Underlying  these  Tests;  65.  The  Tests  and  Their  Results; 

66.  Interpretation  of  the  Results;   67.  The  Influence  of  the  Fireman 167 

CHAPTER  IX. 

SPARK   LOSSES. 

68.    Sparks;  69.  The  Spark  Trap;  70.  Conditions  affecting  Tests;  71.  Observed 
Weight  of  Sparks;  72.  The  Heating  Value  of  the  Sparks;  73.  Volume  of 


CONTENTS.  vii 


PAGE 


Sparks  as  Dependent  upon  Quality  of  Fuel;  74.  Refuse  Caught  in  the 
Ash-pan;  75.  Distribution  of  Sparks  throughout  the  Stack;  76.  The  Size 
of  Sparks;  77.  Conclusion 173 


CHAPTER  X. 

RADIATION    LOSSES. 

78.  The  Amount  of  Heat  Radiated;  79.  Loss  of  Heat  from  a  Locomotive  Stand- 
ing in  a  Building;  80.  Radiation  Losses  upon  the  Road;  81.  Plan  of  the 
Tests;  82.  The  Experimental  Boiler  and  its  Equipment;  83.  Observers; 
84.  The  Track;  85.  Movement  during  the  Tests;  86,  The  Coverings  Tested; 
87.  The  Tests;  88.  Standing  Tests  and  Results;  89.  Running  Testa  and 
Results;  90.  Conditions  Affecting  Results  for  Which  No  Corrections  Have 
Been  Applie' 1 ;  91.  A  Summary  of  Results;  92.  Efficiency  of  Coverings;  93. 
Radiation  and  Its  Power  and  Coal  Equivalent;  94.  The  Effect  of  Condi- 
tions Other  than  Those  Which  Prevailed  during  the  Tests;  95.  Conclusions.  185 


CHAPTER  XL 

THE  FRONT  END. 

96.  Definitions;  97.  Draft  and  Its  Distribution;  98.  The  Action  of  the  Exhaust- jet; 
99.  Form  and  Character  of  the  Jet;  100.  The  Jet  as  Affected  by  Changes  in 
Speed  of  the  Locomotive;  101.  The  Effect  upon  the  Jet  of  Changes  in  the 
Height  of  the  Bridge;  102.  Jets  Formed  by  a  Steady  Blast  of  Steam;  103.  The 
Form  of  the  Jet  as  Influenced  by  Different  Tips;  104.  The  Form  and  Efficiency 
of  the  Jet  as  Affected  by  Bars  over  the  Tip;  105.  The  Form  of  the  Jet  as  Af- 
fected by  Stack  Proportions;  106.  The  Jet  as  Affected  by  Cut-off ;  107.  The 
Stack  Problem;  108.  The  Plan  of  the  Tests;  109.  Conditions  at  the  Grate;  110. 
The  Experimental  Stacks  and  Nozzles;  111.  The  Tests;  112.  Results;  113. 
A  Basis  of  Comparison;  114.  The  Effect  upon  Stack  Proportions  of  Changes 
in  Speed  and  Cut-off;  115.  A  Review  of  Best  Results;  116.  Relation  of 
Height  to  Diameter  of  Stack;  117.  The  Effect  of  Changes  in  the  Height  of 
the  Exhaust  Nozzle  upon  the  Diameter  of  the  Stack;  118.  Equations  Giving 
Stack  Diameters  for  Any  Height  of  Stack  between  the  Limits  of  26  Inches 
and  56  Inches,  and  Any  Height  of  Nozzle  between  the  Limits  of  10  Inches 
below  the  Center  of  the  Boiler  and  20  Inches  above  the  Center  of  the  Boiler, 
and  for  Any  Diameter  of  Front  End;  119.  Unavoidable  Loss  in  Draft  with 
Reduction  in  Height  of  Stack;  120.  Relative  Advantage  of  Straight  and 
Tapered  Stacks;  121.  A  Summary  of  Results;  122.  Later  Experiments  ...  209 


CHAPTER  XII. 

SUPERHEATING    IN   THE    SMOKE-BOX. 

123.    An  Experimental  Determination ,....,. .   262 


viii  CONTENTS. 


IV.   THE  ENGINES. 

CHAPTER  XIII. 

INDICATOR  WORK. 

PAGE 

124.  Concerning  Indicator  Work;  125.  The  Effect  upon  the  Diagram  of  Long 
Pipe  Connections  for  Steam-engine  Indicators;  126.  Experiments  upon  a 
Stationary  Engine;  127.  Different  Lengths  of  Pipe;  128.  The  Form  of  the 
Cylinder  Diagrams;  129.  The  Effect  of  the  Pipe  at  Different  Speeds;  130. 
The  Effect  of  the  Pipe  at  Different  Cut-offs;  131.  Conclusions 267 

CHAPTER  XIV. 

THE  EFFECT  OF  LEAD  UPON  LOCOMOTIVE  PERFORMANCE. 

132.  Lead;  133.  Tests  Involving  Different  Amounts  of  Lead;  134.  Effect  of 
Lead  upon  the  Events  of  the  Stroke;  135.  Effect  of  Lead  upon  Valve 
Travel  and  Port  Opening;  136.  Effect  of  Lead  upon  the  Form  of  Indicator 
Cards;  137.  Steam  Consumption;  138.  Lead  and  Machine  Friction;  139. 
Conclusions 282 

CHAPTER  XV. 

THE    EFFECT   UPON    LOCOMOTIVE    PERFORMANCE    OF    OUTSIDE    LAP. 

140.  Outside  Lap;  141.  Events  of  Stroke;  142.  Changes  of  Form  in  the  Indi- 
cator Cards  Resulting  from  Changes  in  Outside  Lap;  143.  Power  Variation; 
144.  Steam  Consumption 291 

CHAPTER  XVI. 

THE    EFFECT   UPON   LOCOMOTIVE    PERFORMANCE    OF   INSIDE    CLEARANCE. 

145.  Inside  Clearance;  146.  Maximum  Opening  of  Steam-port  into  Exhaust; 
147.  Changes  in  Events  of  Stroke  Resulting  from  Inside  Clearance;  148. 
Changes  in  the  Form  of  the  Indicator  Cards  Resulting  from  Inside  Clear- 
ance; 149.  The  Blowing-through  Effect;  150.  Mean  Effective  Pressure; 
151.  Steam  Consumption  as  Affected  by  Increased  Clearance.  -. 298 

CHAPTER  XVII. 

LOCOMOTIVE   VALVE-GEARS. 

152.  The  Function  of  a  Valve-gear;  153.  A  Stephenson  Valve-gear;  154.  What 
the  Stephenson  Gear  Does;  155.  Devices  for  Increasing  the  Acceleration  of 
the  Valve;  156.  Wire-drawing  as  a  Factor  Controlling  Valve-gear  Design; 


CONTENTS.  IX 

PAGE 

157.  Improved  Valve-gears;   158.  Foreign  Valve-gears;   159.  Adaptability 

of  Valve-gears;    160.  The  Conclusion 310 

CHAPTER  XVIII. 

ACTION    OF   THE    COUNTERBALANCE. 

161.  The  Problem  of  Balancing;  162.  Experimental  Method;  163.  The  Balance 

of  the  Locomotive;    164.  Results;    165.  Conclusions 321 

CHAPTER  XIX. 

MACHINE   FRICTION. 

166.  A  Statement  of  the  Problem;  167.  Methods;  168.  Difficulties  Encoun- 
tered in  Measuring  Draw-bar  Stresses;  169.  Friction  Tests  and  Their  Results; 
170.  A  Comparison  of  Results;  171.  Conclusions 333 


V.   LOCOMOTIVE   PERFORMANCE. 

CHAPTER  XX. 

THE    EFFECT    OF   THROTTLING. 

172.  Throttling;  173.  The  Tests;  174.  Indicator  Cards;  175.  Numerical  Re- 
sults; 176.  Steam  Consumption;  177.  Machine  Friction 352 

CHAPTER  XXI. 

EFFECT    OF  HIGH  STEAM    PRESSURES    ON    LOCOMOTIVE    PERFORMANCE. 

178.  Power  and  Efficiency;  179.  Thermal  Advantage  of  High  Steam  Pressures; 
180.  The  Arguments  for  and  against  the  Use  of  Higher  Pressures;  181. 
Tests  at  Different  Pressures;  182.  Pressure  versus  Capacity;  183.  Summary.  363 

CHAPTER  XXII. 

CONCERNING   DIAMETER   OF  DRIVING-WHEELS. 

184-  Practice  with  Reference  to  Wheel  Diameters;    185.  A  Study  Based  upon 

Observed  Facts;    186.  A  Recapitulation 373 

CHAPTER  XXIII. 

ATMOSPHERIC   RESISTANCE    TO    THE   MOTION    OF    RAILWAY    TRAINS. 

187.  Atmospheric  Resistance;  188.  The  Plan  of  the  Experiments;  189.  Con- 
duit; 190.  Air  Supply;  191.  The  Determination  of  the  Velocity  of  the  Air 


CONTENTS. 

PAGE 

Currents;  192.  The  Model  Cars;  193.  Observations;  194.  Observed  and 
Calculated  Results;  195.  One  Model;  196.  Two  Models;  197.  Trains  of 
Three,  Five,  Ten,  and  Twenty-five  Models;  198.  The  First  Model  of  a 
Train;  199.  The  Last  Model  of  a  Train;  200.  The  Second  Model  of  a  Train; 
201.  Models  between  the  Second  and  Last  of  a  Train;  202.  Distribution  of 
Forces  Acting  throughout  the  Length  of  the  Model  Train;  203.  Relation 
of  Force  and  Velocity;  204.  A  Summary  of  Conclusions;  205.  Atmospheric 
Resistance  to  Actual  Trains;  206.  Application  of  Results  Obtained  from 
Models;  207.  Resistance  Offered  to  Locomotive  and  Tender;  208.  Resist- 
ance Offered  to  Trains  of  Freight  Cars;  209.  Resistance  Offered  to  Trains 
of  Passenger  Cars;  210.  Resistance  Offered  to  Any  Train  in  Terms  of  Its 
Length;  211.  Conclusions 377 


CHAPTER  XXIV. 

A  GENERALIZATION  CONCERNING  LOCOMOTIVE  PERFORMANCE. 

212.  Application  of  Data;  213.  Boiler  Performance;  214.  Cylinder  Perform- 
ance; 215.  Draw- bar  Pull;  216.  Losses  between  Cylinder  and  Draw- bar; 
217.  The  Application  of  Results  to  Several  Typical  Locomotives;  218.  A 
Summary  of  Results 411 


ILLUSTRATIONS. 


no.  PAQB 

1.  The  Purdue  Locomotive,  Schenectady  No.  1 3 

2.  The  Course  Followed  from  Track  to  Laboratory 4 

3.  The  Engineering  Laboratory,  1891 5 

4.  Plan  of  the  Engineering  Laboratory 5 

5.  The  Locomotive  in  the  Laboratory,  1891-94 6 

6.  Elevation  of  Locomotive  Mounting 8 

7.  Plan  of  Locomotive  Mounting 10 

8.  The  Exhaust-fan  above  the  Engine 12 

9.  Supporting  Axles 13 

10.  Alden  Friction-brake 14 

11.  Arrangement  for  Oil  Circulation 15 

12.  Friction-brake  with  One-half  of  Case  Removed 16 

13.  Locomotive  Dynamometer 19 

14.  The  Dynamometer  and  ihe  Mechanism  for  Controlling  Pressure  on  Brakes  .  ,  22 

15.  The  Completed  Engineering  Laboratory  prior  to  January  23,  1904 24 

16.  The  Locomotive  Testing  Plant  Immediately  after  the  Fire 25 

17.  Elevation  of  the  Second  Testing  Plant 26 

18.  Plan  of  the  Second  Testing  Plant 28 

19.  The  Dynamometer  and  the  Mechanism  for  Controlling  Pressure  on  Brakes, 

Second  Plant. 29 

20.  Section  of  Building,  Second  Plant . .  ; 32 

21.  Floor  Plan,  Second  Plant 33 

22.  An  Interior  View,  Second  Plant. 35 

23.  24.  Locomotive  Laboratory,  1894 37,  38 

25.  Plan  of  the  Reconstructed  Engineering  Laboratory 38 

26.  The  Departure  of  Schenectady  No.  1 39 

27.  Schenectady  No.  1  in  a  New  Role 39 

28.  The  Second  Experimental  Locomotive,  Schenectady  No.  2 40 

29.  Elevation  of  Schenectady  No.  1 46 

30.  Stack 53 

31.  Exhaust-pipe  and  -nozzle 53 

32.  Dry  Pipe 54 

xi 


xii  ILLUSTRATIONS. 

FIG.  PAGE 

33.  Branch  Pipe ; , 54 

34.  Netting  and  Deflector-plate 55 

35.  Boiler 56 

36.  Cylinder  and  Saddle 57 

37.  Valve-box  and  Cover 58 

38.  Cylinder-heads 59 

39.  Piston  and  Piston-rod 60 

40.  Cross-head 60 

41.  Guides  and  Guide-yoke 61 

42.  Valve .' 62 

43.  Valve-yoke 62 

44.  Steam-chest  Valve-rod 62 

45.  Rocker 63 

46.  Link  and  Link  Block 63 

47.  Eccentric  Rod 64 

48.  Eccentric  Strap 64 

49.  Eccentric 65 

50.  Reverse-shaft 65 

51.  Reverse-lever  and  Quadrant 66 

52.  Throttle -lever 66 

53.  Throttle  and  Throttle-pipe 67 

54.  Steam-passage  Areas 68 

55.  Running  Log 70 

56.  Feed-water  Log 71 

57.  Fuel  Log 72 

58.  Calorimeter  Log 73 

59.  Indicator  Record 74 

60.  Summary  Sheet 75 

61.  Indicator- cards,  showing  Effect  of  Speed  and  Cut-off 104 

62.  Indicator-cards,  showing  Effect  of  Speed  upon  Size  of  Card 105 

63.  Diagram  showing  Mean  Effective  Pressure 108 

64.  Diagram  showing  Indicated  Horse-power 109 

65.  66.  Diagram  showing  Steam  per  I.H.P.  per  Hour 110,  111 

67.  Diagram  showing  Percentage  of  Total  Steam  Accounted  for  by  Indicator.  .  .    113 

68.  Diagram  showing  Percentage  of  Total  Steam  Accounted  for  by  Indicator  at 

Cut-off 114 

69.  Diagram  showing  Equivalent  Evaporation  per  Hour 116 

70.  Diagram  showing  Evaporative  Efficiency 117 

71.  Diagram  showing  Coal  per  I.H.P.  per  Hour 119 

72.  Diagram  showing  Coal  per  D.H.P.  per  Hour 120 

73.  Diagram  showing  Draw-bar  Pull 120 

74.  Diagram  showing  Dynamometer  Horse-power 121 

75.  Diagram  showing  Friction  Horse-power 121 

76.  Diagram  showing  Coal  per  Mile-run 122 

77.  Chart  from  Recording-gauge  showing  Boiler  Pressure 127 

78.  Chart  from  Recording-gauge  showing  Draft 139 

79.  Chart  from  Recording-gauge  showing  Back  Pressure 140 


ILLUSTRA  TIONS.  xiii 


FIG. 

80.  Diagram  showing  Coal  per  Foot  of  Grate  Surface,  as  Related  to  Draft  and 

Smoke-box  Temperature  ..........................................  141 

§1.  Diagram  showing  Water  per  Foot  of  Heating-surface,  as  Related  to  Draft 

and  Smoke-box  Temperature  ......................................  142 

82.  Diagram  showing  Rate  of  Evaporation  and  Evaporative  Efficiency  .......    144 

83.  Diagram   showing   Rate  of  Evaporation  and   Evaporative    Efficiency  as 

Obtained  from  Five  Samples  of  Bituminous  Coal  ....................  150 

84.  Diagram  showing  Relation  of  Coal  Burned  and  Water  Evaporated  ........  152 

85.  Diagram  showing  Rates  of  Combustion  and  Evaporative  Efficiency  .......  153 

86.  Grate  used  in  Test  2  ................................................  158 

87.  Grate  used  in  Test  3  ................................................  158 

88.  Grate  used  in  Test  4  ................................................  158 

89.  Diagram  showing  Evaporative  Efficiency  and  Rate  of  Combustion.  *  ......  164 

90.  Diagram  showing  Losses  in  Evaporative  Efficiency  ......................  165 

91.  Diagram  showing  Evaporative  Efficiency  Obtained  as  a  Result  of  Thick 

Firing  as  Compared  with  a  Curve  of  Normal  Efficiency  ...............   170 

92.  Spark-  trap  ........................................................    174 

93.  Plan  of  Stack,  with  Assumed  Divisions  Employed  in  Determining  Spark-losses  175 

94.  Diagram  showing  Spark-losses  ..........................  .  ............    177 

95.  Diagram  showing  Heating  Value  of  Sparks  .............................    179 

96.  Pounds  of  Sparks  Passing  out  of  Stack  per  Hour  ..............  .  .........   183 

97.  Pounds  of  Sparks  Passing  out  through  Areas  Indicated  ..................    183 

98.  Cross-section  of  Stack  showing  Density  of  Spark  Discharge  ...............   183 

99.  Sample  Sparks  .....................................................    184 

100.  Head  of  Experimental  Train  .........................................  187 

101.  Experimental  Boiler  ................................................  189 

102.  Diagram  showing  Effect  of  Speed  on  Radiation  Loss  ...................  206 

103.  Diagram  showing  Distribution  of  Draft  ................................  210 

104.  Apparatus  Used  in  Exploring  the  Exhaust-  jet  ..........................  213 

105.  The  Form  of  the  Jet  ................................................  216 

106.  A  Diagrammatic  Illustration  of  the  Process  of  Envelopment  by  the  Jet.  .  .  .  217 
107-109.  Form  and  Character  of  the  Jet  as  Affected  by  Changes  in  Speed  of  the 

Locomotive,  Low-bridge  Pipe.  ...  ..............................  219 

110-112.  Form  and  Character  of  the  Jet  as  Affected  by  Changes  in  Speed  of  the 

Locomotive,  High-bridge  Pipe.  .  .  ...............................   221 

113-1  15.  Form  and  Character  of  the  Jet  as  Affected  by  a  Steady  Flow  of  Steam  .  .  222 
116-118.  Form  and  Character  of  the  Jet  as  Affected  by  External  Conditions.  .  .  .  223 

119.  Three  Forms  of  Exhaust-tips  .........................................  224 

120.  Bars  or  Bridges  for  Exhaust-tips  .......................................  225 

121.  The  Fire-box  as  Prepared  for  Tests  of  Stacks  ...........................  228 

122.  Dimensions  of  Stacks  Employed  in  Experiments  ........................  229 

123.  Dimensions  of  Exhaust-nozzles  Employed  in  Experiments  ...............  229 

124.  Design  of  Exhaust-pipe  and  -nozzle  ...................................   230 

125.  Diagram  showing  Draft  Obtained  from  a  Straight  Stack  26£"  High  and  of 

Various  Diameters  ...  ...........................................   237 

126.  Diagram  showing  Draft  Obtained  from  a  Straight  Stack  36£''  High  and  of 

Various  Diameters  ..............  .........  ...  237 


Xiv  ILLUSTRATIONS. 

FIG-  PAGE 

127.  Diagram  showing  Draft  Obtained  from  a  Straight  Stack  46|"  High  and  of 

Various  Diameters 238 

128.  Diagram  showing  Draft  Obtained  from  a  Straight  Stack  56|"  High  and  of 

Various  Diameters 238 

129.  Diagram  showing  Draft  Obtained  from  a  Tapered  Stack  26£"  High  and  of 

Various  Diameters 238 

130.  Diagram  showing  Draft  Obtained  from  a  Tapered  Stack  36£"  High  and  of 

Various  Diameters 238 

131.  Diagram  showing  Draft  Obtained  from  a  Tapered  Stack  46£"  High  and  of 

Various  Diameters 239 

132.  Diagram  showing  Draft  Obtained  from  a  Tapered  Stack  56|"  High  and  of 

Various  Diameters 239 

133.  Diagram  showing  Combination  of  Stack  Diameter  and  Nozzle  for  Best  Results 

Obtainable  from  a  Straight  Stack  26£"  High 242 

134.  Diagram  showing  Combination  of  Stack  Diameter  and  Nozzle  for  Best  Re- 

sults Obtainable  from  a  Straight  Stack  36£"  High 242 

135.  Diagram  showing  Combination  of  Stack  Diameter  and  Nozzle  for  Best  Re- 

sults Obtainable  from  a  Straight  Stack  46|"  High 242 

136.  Diagram  showing  Combination  of  Stack  Diameter  and  Nozzle  for  Best  Re- 

sults Obtainable  from  a  Straight  Stack  56£"  H'gh 242 

137    Diagram  showing  Combination  of  Stack  Diameter  and  Nozzle  for  Best  Re- 
sults Obtainable  from  a  Tapered  Stack  26  \"  High 243 

138.  Diagram  showing  Combination  of  Stack  Diameter  and  Nozzle  for  Best  Re- 

sults Obtainable  from  a  Tapered  Stack  36£"  High 243 

139.  Diagram  showing  Combination  of  Stack  Diameter  and  Nozzle  for  Best  Re- 

sults Obtainable  from  a  Tapered  Stack  46£"  High 243 

140.  Diagram  showing  Combination  of  Stack  Diameter  and  Nozzle  for  Best  Re- 

sults Obtainable  from  a  Tapered  Stack  56|"  High 243 

141.  Diagram  showing  Relation  of  Height  to  Diameter  of  Stack  for  Best  Results .  246 

142.  Proportions  for  Tapered  Stack  and  Nozzle 250 

143.  Proportions  for  Straight  Stack  and  Nozzle 251 

144_147.  Diagrams  showing  Relation  of  Draft  to  Height  of  Stack 252 

148.  The  Best  Arrangement  of  Front  End  assuming  an  Outside  Tapered  Stack 

29"  High 259 

149.  The  Best  Arrangement  of  Front  End  assuming  an  Inside  Stack  of  Usual 

Form,  Outside  Projection  29" 259 

150.  The  Best  Arrangement  of  Front  End  assuming  a  False  Top  with  Stack  having 

an  Outside  Projection  of  29" 259 

151.  The  Best  Arrangement  of  Front  End  assuming  a  Modified  Form  of  Inside 

Stack 260 

152.  The  Best  Arrangement  of  Front  End  assuming  an  Inside  Stack  with  Bell.  .   260 

153.  The  Best  Arrangement  of  Front  End  assuming  a  Single  Draft-pipe 260 

154.  The  Best  Arrangement  of  Front  End  assuming  a  Double  Draft-pipe 260 

155.  A  Proposed  Standard  Front  End 261 

156.  Points  Selected  for  Observing  Degree  of  Superheating  in  Smoke-box 263 

157.  Thermometer  Cup 264 

158.  Indicator  Rigging 268 


ILLUSTRATIONS.  xv 

FIG.  PAGE 

159.  Long  and  Short  Pipe  Connections  for  Locomotive  Indicators 269 

160.  Typical  Cards  from  Indicators  Differently  Connected  with  a  Locomotive 

Cylinder 270 

161.  Arrangement  of  Pipes  and  Indicators  on  Buckeye  Engine 272 

162.  Pipe  and  Cylinder  Indicator- cards,  Five-foot  Pipe,  200  R.P.M 274 

163.  Pipe  and  Cylinder  Indicator-cards,  Ten-foot  Pipe,  200  R.P.M 274 

164.  Pipe  and  Cylinder  Indicator-cards,  Fifteen-foot  Pipe,  200  R.P.M. 274 

165.  The  General  Effect  upon  the  Form  of  Indicator-cards  of  Very  Long  Pipes .  .  275 

166.  Pipe  and  Cylinder  Indicator-cards,  Ten-foot  Pipe,  100  R.P.M 278 

167.  Pipe  and  Cylinder  Indicator-cards,  Ten-foot  Pipe,  200  R.P.M 278 

168.  Pipe  and  Cylinder  Indicator-cards,  Ten-foot  Pipe,  300  R.P.M 278 

169.  Pipe  and  Cylinder  Indicator-cards,  Ten-foot  Pipe,  200  R.P.M.,  -|  Cut-off.  .  280 
1-70.  Pipe  and  Cylinder  Indicator-cards,  Ten-foot  Pipe,  200  R.P.M.,  J  Cut-off.  .  180 

171.  Pipe  and  Cylinder  Indicator- cards,  Ten-foot  Pipe,  200  R.P.M.,  £  Cut-off.  .  ^80 

172.  Events  of  Stroke  as  Affected  by  Changes  in  Lead 285 

173.  Device  for  Measuring  Valve  Travel 286 

174.  Indicator-cards  from  Tests  for  which  there  were  Changes  in  Lead 288 

175.  Indicator-cards  showing  the  General  Effect  of  Changes  in  Lead 289 

176.  Steam  Consumption  as  Affected  by  Lead 289 

177.  Valves  having  Different  Amounts  of  Outside  Lap 292 

178.  179.  Valve  Diagrams 294 

180-182.  Indicator-cards  from  Tests  for  which  there  were  Changes  in  Outside  Lap  295 

183.  Indicator-cards  showing  the  General  Effect  of  Outside  Lap 296 

184.  Valve  having  Different  Amounts  of  Inside  Clearance 299 

185.  Diagram  of  Tests  to  Determine  the  Effect  of  Inside  Clearance 300 

186.  187.  Indicator-cards  from  Tests  for  which  there  were  Changes  in  Clearance  302, 303 

188.  Diagram  showing  Exhaust  Interference  with  Excessive  Clearance 304 

189,  190.   Diagram  showing  Inside  Clearance  and  Steam  Consumption 307,  COS 

191.  Valve-motion  Diagram 312 

192.  'Indicator-cards  representing  Different  Speeds  and  Cut-offs 314 

193.  Stationary  Link 317 

194.  Allen  Link 317 

195.  Joy  Gear 318 

196.  Walschaert  Gear 318 

197.  Arrangement  of  Guide-pipe  and  -wire  for  Counterbalance  Experiments  ....   32 j 

198.  Initial  End  of  Test  Wire 324 

199.  Diagram  of  Revolving  and  Reciprocating  Parts 324 

200-202.  Plotted  Measurements  of  Wires 325,  326 

203,  204.    Diagram   having  Reference   to   Position   of  Drivers   on   Supporting 

Wheels 336,  337 

205.  Tell-tale  showing  Position  of  Locomotive  on  the  Mounting  Mechanism 339 

206.  Method  of  Supporting  Locomotive  during  Friction  Tests 342 

207.  Diagram  showing  Draw-bar  Pull  Due  to  Engine  Position 343 

208.  Diagram  showing  Tests  Run  under  Throttle 353 

209-212.  Indicator-cards  from  Tests  Run  under  Throttle 354-357 

213.  Diagram  showing  Steam  Consumed  when  Running  under  Throttle 359 

214.  Diagram  showing  Steam  Consumption  under  Different  Pressures 366 


xvi  ILLUSTRATIONS. 

FIG.  PAGE 

215.  Diagram  showing  Economy  Resulting  from  Increase  in  the  Capacity  of 

Boiler. 369 

216.  Section  of  Conduit  within  which  Model  Trains  were  Exposed  to  the  Action  of 

Air-currents 379 

217.  Pitot's  Tube 379 

218.  The  Pitot  Tube  as  Used  in  Experiments 380 

219.  A  Portion  of  the  Conduit  with  Attached  Tubes 381 

220.  Diagram  showing  Velocities  at  Several  Points  in  the  Cross-section  of  the 

Conduit 382 

221.  The  Model  Dynamometer  Car 383 

222.  Elevation  of  Model  Train 385 

223.  A  View  \vithin  the  Conduit 386 

224.  The  Influence  of  the  Air-currents  upon  Different  Portions  of  the  Model 

Train v 396 

225.  Diagram  showing  Resistance  of  Different  Portions  of  a  Train  at  Different 

Speeds 397 

226.  Diagram  showing  Relation  of  Draw-bar  Stress  to  Speed 416 

227.  Diagram  showing  Losses  between  Cylinders  and  Draw-bar 419 

228.  Diagram  showing  Absorption  of  Power  between  Cylinders  and  Draw-bar, 

and  Traction  Power 4'21 

229.  Diagram  showing  the  Performance  at  the   Draw-bar   of   Several   Typical 

Locomotives 422 


A 

UNIVERSITY 

T  f 


LOCOMOTIVE  PERFORMANCE. 

I.   LOCOMOTIVE  TESTING. 

CHAPTER  I. 
THE    DEVELOPMENT    OF    THE    PURDUE    TESTING-PLANT. 

1.  The  Growth  of  Engineering  Laboratories  at  Purdue.' — Purdue 
University   was  opened   as   a  school   of   Science,   Agriculture,   and 
Mechanic  Arts  in  1874.    Five  years  later  instruction  was  given  students 
in  shop-practice,  and  in  1882  a  regular  four-years  course  in  Mechan- 
ical  Engineering    was    established.     From    this    time    there    was    a 
gradual  increase  in  the  amount  of  apparatus  available  for  the  use 
of   engineering    students,  but  it  was  not  until  ten  years  after  the 
establishment  of  the  courses  in  shop-work  that  the  development  of 
an  engineering  laboratory  was  entered  upon. 

In  the  spring  of  1890  the  policy  with  reference  to  the  equipment 
of  such  a  laboratory  found  expression  in  an  order  given  for  a  cross- 
compound  Corliss  engine  which  during  the  summer  of  that  year 
was  established  as  a  complete  testing-plant  with  condenser,  air- 
pump,  weighing -tanks,  and  all  other  accessory  apparatus  needful 
for  experimental  work.  A  year  later,  in  1891,  a  considerable  sum 
of  money  became  available  for  use  in  the  extension  of  laboratory 
facilities,  and,  with  a  view  to  future  development,  plans  for  an  exten- 
sive building  were  adopted.  Two  important  results  followed:  one 
consisting  in  the  erection  of  a  portion  of  the  building  which  had 
been  planned,  and  the  other  in  the  establishment  of  a  locomotive 
testing-plant  as  a  part  of  its  equipment. 

2.  Considerations   Leading    to   a   Locomotive   Testing-plant. — 
The  locomotive  testing-plant  was  the  outgrowth  of  natural  condi- 


2  LOCOMOTIVE  PERFORMANCE, 

tions.  The  Trustees  and  the  President  of  the  University  had  already 
shown  their  interest  in  the  development  of  laboratories  for  engi- 
neering students,  and  it  was  easy  for  them  to  foresee  the  great  advan- 
tage to  be  derived  from  a  study  of  locomotive  performance  under 
conditions  as  favorable  to  the  work  of  testing  as  those  which  had 
been  so  often  declared  necessary  in  connection  with  stationary 
engines.  It  was  known  that  under  conditions  of  service  locomotives 
were  tested  with  difficulty,  results  being  far  less  satisfactory  than  similar 
results  obtained  from  stationary  engines  under  service  conditions. 
If,  in  stationary  practice,  progress  had  been  made  by  the  establish- 
ment of  experimental  plants,  how  much  more  might  be  achieved  by 
the  installation  of  experimental  locomotives! 

These  and  similar  arguments  made  it  clear  that  the  process  of 
building  up  the  equipment  of  an  extensive  engineering  laboratory 
might  easily  and  logically  be  made  to  involve  the  erection  of  a  loco- 
motive testing-plant,  the  value  of  which  both  as  a  means  to  the 
instruction  of  students  and  for  the  purposes  of  research  could  not 
be  doubted. 

The  general  outlines  of  the  plant  having  been  defined,  its 
design  and  establishment  became  largely  a  matter  of  routine.  The 
locomotive,  stripped  of  the  enchantment  which  may  perhaps  attend 
it  on  the  road,  became  simply  a  steam-engine  and  a  steam-boiler. 
Its  action  was  not  different  in  principle  from  that  of  other  engines 
and  boilers  already  included  in  the  plans  of  the  laboratory,  and  hence 
great  experience  in  the  management  of  locomotives,  as  such,  was  not 
necessary.  In  fact,  the  Purdue  staff,  which  was  instrumental  in 
establishing  the  plant,  had  no  member  who  had  been  trained  in 
the  motive-power  department  of  a  railroad. 

3.  Arrival  of  the  Locomotive. — In  September,  1891,  the  loco- 
motive which  had  been  named  for  its  builders,  "Schenectady," 
arrived  upon  a  switch  of  the  Lake  Erie  &  Western  Railway  about 
one  mile  distant  from  the  laboratory,  and  at  a  point  having  approxi- 
mately the  same  elevation  with  the  University  grounds.  There 
was  no  track  to  the  laboratory.  The  surface  of  the  ground  between 
it  and  the  laboratory  which  was  to  be  traversed  was  slightly  rolling, 
and  from  a  considerable  portion  of  the  intervening  territory  a  wheat- 
crop  had  been  taken  eight  or  ten  weeks  previous  to  the  arrival  of 
the  engine. 

The  delivery  of  the  engine  upon  the  switch  aroused  great  enthu- 
siasm on  the  part  of  the  students  of  Purdue,  and  out  of  respect  for 


THE  DEVELOPMENT  OF   THE  PURDUE    TESTING-PLANT.     3 

the  interest  shown  a  holiday  was  declared,  and  a  call  was  made  for 
volunteers  to  assist  in  receiving  the  engine  and  in  starting  it  on  its 
overland  journey.  It  was  rather  late  in  the  morning  before  the 
work  began.  The  privilege  of  breaking  a  joint  in  the  track,  to  assist 
in  rolling  the  engine  out  upon  the  temporary  skids  which  had  been 
prepared,  having  been  denied,  it  was  found  necessary  to  block  and 
carry  the  flange  of  the  wheels  over  the  top  of  the  switch-rails,  a  task 
which  involves  some  difficulty  even  when  managed  by  experienced 
men  with  plenty  of  tools,  whereas  in  the  case  described  both  experi- 
ence and  tools  were  lacking.  But  many  willing  hands,  aided  by  a 
single  team  of  horses,  made  light  work  of  what  might  otherwise  have 
been  a  laborious  undertaking,  and  when  night  arrived  "  Schenectady  " 


PIG.  1.  -The  Purdua  Locomotive,  Schenectady  No.  1. 

had  been  pulled  across  the  right-of-way  ditch  and  well  out  toward 
the  middle  of  the  first  field. 

By  the  close  of  the  first  day  the  measure  of  the  task  had  been 
taken  and  time  was  therefore  given  to  a  reconstruction  of  equipment. 
Three  sections  of  track  were  made,  each  of  a  rail's  length,  built  in 
the  form  of  skids  and  capped  by  56-pound  rails.  The  foundation  of 
each  consisted  of  two  5X12  yellow-pine  pieces,  laid  flatwise,  across 
which  2X12  pieces  were  spaced  as  ties,  the  rail-spikes  passing  through 
the  ties  and  into  the  foundation  beneath.  The  reorganized  force 
included  three  pairs  of  horses  with  drivers  and  two  or  three  men  to 
handle  blocking.  One  pair  of  horses  was  employed  to  give  forward 
movement  to  the  engine ;  a  second  to  draw  the  skids  one  after  another 
from  rear  to  front ;  and  the  third  to  pull  the  heel  of  the  advancing  skid 


LOCOMOTIVE  PERFORMANCE 


into  line  with  the  one  previously  placed.  The  men  soon  became 
so  skilled  in  their  respective  parts  that  where  the  ground  was  smooth 
the  engine  could  be  kept  in  constant  motion  for  considerable  dis- 
tances, one  skid  being  drawn  from  rear  to  front  and  placed  in  posi- 
tion while  the  engine  was  passing  over  the  other  two. 

Even  with  the  new  apparatus  it  was  found  impossible  to  make 
the  locomotive  follow  the  skids  if  laid  on  a  curve,  and  wrherever  a 
change  of  direction  was  necessary  it  was  made  by  laying  cross- 
blocking  under  the  skids,  upon  which  one  end  of  the  skid  bearing 
the  engine  was  slipped  bodily.  The  course  involved  four  turns, 
each  somewhat  less  than  a  right  angle,  and  the  whole  distance 


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FIG.  2. — The  Course  followed  from  Track  to  Laboratory. 

traversed  by  the  engine  was  in  the  neighborhood  of  \\  miles.  On 
the  eighth  working  day  after  the  start,  the  engine  arrived  at  the 
laboratory  without  accident  and  without  having  once  touched  the 
ground.  * 

4.  The  First  Testing-plant.— It  has  been  already  noted  that 
before  the  locomotive  was  ordered,  lines  had  been  laid  down  for  an 
extensive  engineering  laboratory,  and  the  construction  of  a  portion 
of  this  had  been  entered  upon  early  in  the  spring  of  1891.  The 
building  thus  begun  constituted  a  definite  portion  of  the  larger  struc- 

*  The  success  attending  the  transportation  was  chiefly  due  to  the  skill  and 
energy  of  Mr.  Robert  Lackey,  who  had  immediate  charge  of  the  operations  after 
the  first  day's  work.  Mr.  Lackey  at  the  time  was  a  student-assistant  in  the  labora- 
tory. By  his  good  judgment  an  undertaking  which,  if  less  perfectly  managed, 
might  have  been  an  expensive  one,  cost  but  a  trifling  sum. 


O      THF 

UNIVERSITY   ] 


THE   DEVELOPMENT  OF   THE  PURDUE    TESTING-PLANT      5 

ture  of  which  it  was  eventually  to  form  a  part.  A  view  of  this  por- 
tion of  the  building  is  shown  by  Fig.4  3,  and  the  location  of  the 
testing-plant  within  it  by  the  floor-plan,  Fig.  4. 


FIG.  3. — The  Engineering  Laboratory,  1891. 

Between  the  time  of  ordering  the  locomotive  and  its  delivery, 
the  details  of  the  mounting  mechanism  were  designed  and  put  in 
place,  so  that  when,  in  September,  1891,  the  locomotive  arrived,  the 


FIG.  4.— Plan  of  the  Engineering  Laboratory,  1891. 

plant  was  practically  ready  for  its  reception.  The  following  descrip- 
tion of  this  first  locomotive  testing-plant  is  based  upon  a  paper 
presented  before  the  American  Society  of  Mechanical  Engineers.* 

*  "An   Experimental   Locomotive."     Proceedings   of  the  American   Society  of 
Mechanical  Engineers,  1892. 


6 


LOCOMOTIVE  PERFORMANCE 


The  plan  of  mounting,  in  its  inception,  involved  (1)  support- 
ing wheels  carried  by  axles  running  in  fixed  bearings,  to  receive  the 
locomotive  drivers  and  to  turn  with  them;  (2)  brakes  which  would 
have  sufficient  capacity  to  absorb  continuously  the  maximum  power 
of  the  locomotive,  and  which  should  be  mounted  on  the  axles  of 
the  supporting  wheels;  and  (3)  a  traction  dynamometer  of  such 
form  as  would  serve  to  indicate  the  horizontal  moving  force  and  at  the 
same  time  allow  but  a  slight  horizontal  motion  of  the  engine  on  the 
supporting  wheels.  It  was  believed  that  a  locomotive  thus  mounted 
could  be  run  either  ahead  or  aback  under  any  desired  load  and  at 
any  speed;  that  while  thus  run,  its  performance  could  be  deter- 


FIG.  5. — The  Locomotive  in  the  Laboratory,  1891-94. 

mined  with  a  degree  of  accuracy  and  completeness  far  exceeding  that 
which  it  is  possible  to  secure  under  ordinary  conditions  of  the  road; 
and  that  the  whole  apparatus  would  be  extremely  valuable  to  students 
in  steam-engineering.  It  was  not  assumed  that  every  condition  of 
the  track  would  be  perfectly  met,  but  it  was  expected  that  the  results 
obtained  would  prove  valuable  in  extending  a  knowledge  of  loco- 
motive performance. 

Fig.  5  from  a  photograph  is  a  view  of  the  locomotive  in  place 
upon  the  plant;  Fig.  6  shows  a  complete  general  view,  in  elevation, 
of  the  locomotive  and  its  mounting  machinery;  and  Fig.  7  shows 
in  plan  the  mounting  machinery  only. 

Reference  to   these  figures  will  show  that  there  was  a  heavy 


THE  DEVELOPMENT  OF   THE  PURDUE    TESTING-PLANT.     7 

rubble  foundation,  capped  at  convenient  points  with  cut  stones  rising 
10  inches  above  grade-line.  Upon  these  stones  were  placed  well- 
seasoned  oak  timbers  arranged  in  two  lines,  each  composed  of  three 
lengths,  4X14  inches.  The  timbers  of  each  line  were  well  bolted 
to  each  other  and  were  securely  anchored  to  the  foundation.  Upon 
the  timbers  rested  the  bearings  of  the  supporting  axles,  which  were 
thus  given  14  inches  of  oak  to  constitute  an  element  of  elasticity 
between  them  and  the  foundation. 

The  supporting  wheels  were  of  the  same  diameter  with  the  loco- 
motive drivers,  and  similar  in  other  respects  save  that  the  cranks 
and  counterweights  were  omitted.  Their  faces  were  turned  flat, 
with  the  inside  edge  rounded  as  in  a  rail. 

The  four  friction-brakes  which  provided  the  load  for  the  sup- 
porting shafts,  and  which  are  shown  in  position  in  Figs.  6  and  7, 
were  designed  on  the  principle  developed  by  Professor  George  I. 
Alden  and  already  described  by  him.*  The  details  of  the  brake 
design  under  consideration  will  be  given  farther  on,  but  it  is  im- 
portant to  state  here  that  the  principle  as  developed  by  Professor 
Alden  provided  extensive  rubbing  surfaces  of  cast  iron  and  copper. 
Excessive  wear  was  prevented  by  thorough  lubrication.  The  inten- 
sity of  the  brake  action  was  controlled  by  water  pressure,  by  which 
means  the  rubbing  surfaces  were  brought  into  contact  more  or  less 
intimate,  and  the  heat  evolved  was  carried  off  by  water  circulation. 

By  reference  to  the  plan  and  elevation,  Figs.  6  and  7,  it  will  be 
seen  that  there  was  no  provision  for  measuring  the  load  at  the  brakes, 
where,  instead  of  a  weighted  lever,  anchor-rods  were  used  to  secure 
the  case  of  the  brakes  to  the  foundation.  The  value  of  the  load  ap- 
peared at  the  dynamometer  connected  with  the  draw.-bar  of  the  loco- 
motive. The  water  supply  for  the  brakes  was  furnished  by  a  3-inch 
pipe.  It  passed  first  a  balanced  valve  A,  around  which  there  was 
a  by-pass  controlled  by  valve  B.  From  the  tee  C  the  pipe  was 
branched  for  the  several  brakes,  2^-inch  piping  serving  for  two  brakes, 
and  2-inch  for  each  individual  brake.  Valves,  D,  were  provided  in 
the  supply-pipe  for  each  brake,  so  that  any  one  might  be  entirely 
cut  out  or  have  its  action  modified  to  any  desired  extent.  The 
water  from  each  brake  was  returned  by  a  separate  pipe  to  a  point 
E,  where  valves  were  provided  by  which  the  amount  of  water  allowed 
to  pass  each  brake  was  regulated.  From  these  valves  the  water 

*  Transactions  of  the  American    Society  of    Mechanical    Engineers,   Vol.    XI, 
p.  959  et  seq.  »  . 


LOCOMOTIVE  PERFORMANCE. 


THE  DEVELOPMENT  OF   THE  PURDUE    TESTING-PLANT.     9 

flowed  in  an  open  stream  and  was  finally  discharged  into  a  sewer. 
The  water  pressure  within  each  brake  was  indicated  by  one  of  the 
fcur  gauges  at  F,  Fig.  6. 

The  balanced  valve  A  had  its  spindle  connected  with  one  of  the 
levers  of  the  dynamometer  in  such  a  way  that  its  position  was  con- 
trolled by  the  pull,  or  if  backing,  by  the  push  exerted  by  the  loco- 
motive. Thus,  suppose  the  locomotive  to  be  in  motion  and  the 
outlet-valves  at  E  adjusted  to  allow  the  passage  of  enough  water 
to  keep  down  the  temperature  of  the  brakes;  suppose  also  that  the 
pull  of  the  locomotive  were  such  as  to  bring  the  weighted  lever  of 
the  dynamometer  to  its  mid-position,  then  there  would  be  a  defi- 
nite opening  of  the  balanced  valve,  and  a  definite  water  pressure 
within  the  brakes  would  result.  If  now,  for  any  reason,  the  weighted 
lever  should  fall,  there  would  be  a  corresponding  increase  in  the 
opening  of  the  balanced  valve  and,  hence,  an  increase  of  water 
pressure  within  the  brakes.  The  greater  pressure  would  result  in 
greater  resistance  to  the  movement  of  the  supporting  wheels  and, 
hence,  in  a  stronger  pull  of  the  locomotive  on  the  dynamometer, 
and  this  increased  pull  would  tend  to  lift  the  weighted  lever  again. 
Similarly,  if  for  any  reason  the  pull  of  the  locomotive  were  sufficient 
to  raise  the  lever  beyond  its  central  position,  the  balanced  valve 
would  respond  by  reducing  the  water  pressure  within  the  brakes; 
the  tractive  force  of  the  engine  would  then  decrease  and  the  dyna- 
mometer lever  would  fall.  When,  therefore  it  was  desired  to  increase 
the  load  on  the  locomotive  it  was  necessary  only  to  place  the  addi- 
tional weight  upon  the  lever  of  the  dynamometer,  and  the  corre- 
sponding increase  in  the  load  was  furnished  automatically  by  the 
brakes.  By  a  proper  adjustment  of  the  by-pass  valve,  B,  the  lever 
could  be  made  to  stand  exactly  in  its  central  position. 

'The  traction  dynamometer  was  made  up  of  a  system  of  levers. 
The  first  lever  in  the  system,  shown  by  dotted  outline  at  G  in  Figs.  6 
and  7,  had  direct  connection  with  the  locomotive  draw-bar.  The 
last  lever,  shown  at  H,  carried  an  ordinary  weight-holder.  The  whole 
arrangement  was  such  that,  whether  the  engine  moved  ahead  or 
aback,  the  stress  was  transmitted  by  the  draw-bar,  and  its  value 
shown  by  the  weight  necessary  to  balance  the  lever  H. 

The  dynamometer  levers  were  carried  by  a  heavy  framework, 
which  was  well  secured  to  the  locomotive  foundation  and  to  sur- 
rounding parts  of  the  building.  The  character  of  the  framing  is 
but  imperfectly  shown  by  the  drawings. 


10 


LOCOMOTIVE  PERFORMANCE. 


THE  DEVELOPMENT  OF   THE  PURDUE    TESTING-PLANT.   11 

While  the  draw-bar  was  the  only  active  agent  by  which  the 
horizontal  movement  of  the  locomotive  was  controlled,  there  was 
ample  provision  of  chains  and  buffers  to  check  any  excessive  move- 
ment which  might  occur. 

Above  the  levers  of  the  dynamometer  a  floor  was  laid  which 
chiefly  served  the  purposes  of  a  tender.  It  gave  room  for  the  stor- 
age of  a  limited  quantity  of  coal,  and  for  a  tank  from  which  the 
locomotive  injectors  drew  their  supply.  Connected  with  the  water- 
tank  was  a  glass  gauge,  7,  and  above  the  tank  a  weighing-barrel 
through  which  the  tank  received  its  supply.  Scales  for  weighing 
fuel  were  also  given  a  place  on  the  "  tender  floor." 

The  three  counters  at  J  were  connected,  respectively,  with  the 
rear  driving-axle  and  with  each*  of  the  two  supporting  shafts.  These 
gave  a  ready  means  for  determining  the  speed  of  the  engine, 
and  the  per  cent  of  slip  between  the  drivers  and  their  supporting 
wheels. 

The  telltale  at  K  showed  the  position  of  the  locomotive  relative 
to  the  supporting  wheels.  The  board  a  was  fastened  to  the  loco- 
motive and  consequently  moved  with  it;  the  rod  b  was  connected 
at  one  end,  c,  to  an  iron  column  as  a  fixed  point,  and  at  the  other  end 
to  the  pointer  d.  This  pointer  was  pivoted  to  the  board  a  at  e,  so 
that  any  backward  or  forward  movement  of  the  locomotive  was 
greatly  multiplied  in  the  similar  movement  of  the  lower  end  of  the 
pointer  d. 

A  tangent-wheel  and  screw  were  provided  at  L  for  the  purpose 
of  turning  by  hand  the  forward  supporting  axle  and  hence  the 
engine,  whenever  it  might  be  desired  to  do  so,  as,  for  example,  for 
convenience  in  valve-setting.  When  not  in  use,  the  screw  could 
be  disengaged. 

The  truck-wheels  of  the  engine  rested  upon  light  rails  which  were 
fixed  at  the  level  of  the  laboratory  floor  and  extended  in  front  of 
the  engine  a  distance  sufficient  to  allow  the  whole  machine  to  be 
moved  forward  off  the  supporting  wheels,  whenever  the  latter  needed . 
to  be  take  out  for  repairs. 

A  Sturtevant  4JX6J  steam-blower,  located  above  the  engine 
(Figs.  6  and  8)  but  not  in  pipe  connection  with  it,  removed  from  the 
room  everything  given  out  by  the  locomotive  stack,  without  chang- 
ing, materially,  the  draft  conditions  under  which  the  locomotive 
worked. 

The  cylinder-cocks    and   the  overflow-pipes   from   the   injectors 


12 


LOCOMOTIVE  PERFORMANCE. 


were  all  in  loose  connection  with  the  sewer.     The  discharge  from 
the  overflow-pipes  could  be  directed  into  weighing-barrels. 

The  boiler  was  in  pipe  connection  with  the  fixed  boiler  which 
supplied  steam  for  general  use  in  the  laboratory,  so  that  the  loco- 
motive might  be  used  to  supply  steam  to  other  apparatus,  or  the 
fixed  boiler  to  supply  the  locomotive.  In  the  latter  case  the  loco- 
motive boiler  was  drained  by  the  steam-trap  M;  by  this  means  the 
boiler  was  freed  from  water,  and  as  a  consequence  all  its  parts  were 
kept  at  the  same  temperature.  The  greater  convenience  attending 


Stack. 
FIG.  8. — The  Blower  above  the  Engine. 

the  operation  of  the  fixed  boiler  made  its  use  desirable  when  problems 
were  studied  which  affected  only  the  mechanism  of  the  engine. 

The  following  is  a  description  of  some  of  the  more  important 
parts  making  up  the  plant,  the  details  of  which  are  not  clearly  shown 
by  the  drawings  thus  far  referred  to. 

5.  The  Supporting  Axles  were  of  hammered  iron  and  of  the  form 
and  dimensions  shown  by  Fig.  9.  The  bearings  for  these  shafts 
were  8"  in  diameter  and  16"  long.  Each  bearing  was  fitted  to  a 
cast-iron  plate  14"X36"X2",  which  plate,  in  turn,  was  carefully 
bedded  upon  the  oak  timbers  (Figs.  6  and  7).  The  whole  was  made 
secure  by  four  bolts  which  passed  through  the  bearing,  plate,  and 
timber. 


THE  DEVELOPMENT  OF   THE  PURDUE    TESTING-PLANT.   13 


6.  The  Alden  Friction-brakes,  which  supplied  the  load  to  the  sup- 
porting axles  and,  hence,  to  the  locomotive  itself,  are  shown  in 
position  by  Figs.  6  and  7,  and  in  detail  by  Fig.  10.  They  were  designed 
and  constructed  with  the  consent  of  Professor  Alden,  to  whom  the 
author  is  indebted  for  many  courtesies. 

The  cast-iron  moving  disk  K,  Fig.  10,  Sec.  AB,  is  keyed  to  the 
supporting  axle  (not  shown),  and  hence  turns  with  it.  The  power 
of  the  locomotive  is  transmitted  by  the  supporting  wheels  and  axle 
to  the  disk,  on  either  side  of  which  are  light  copper  plates,  L,  which 
form  a  part  of  the  enclosing  case.  The  sides  M  of  this  case  have 


Section  of  rim  at 
Supporting  vheel. 
Of  wheel  03  inches 

d 
li 

< 

hub  of 
imeter 

_  —  jc!  > 

• 

mm 

radius  of  round  corner  %* 
ItoM  of  Wheel                                                        BOM  Of  ^1 

eel  7* 

—  > 

1 

I1 

2  Brake  fit 

journal 

Wlee 
•-£  fit 

smooth  hammered  cot  turned 
sn-allest  Clj.  ti  be  EJt  less  than  7^* 

WheeJ 

Journal  * 

Brake  Ht     |        |        ^ 

5fiI««J_'^_       -,JLg 

For  wormwhcel  on  une  shaft 

> 

not  occupied  on  other 

FIG.  9. — Supporting  Axle;. 

bearing  on  the  hub  of  the  moving  disk,  and  are  connected  around 
their  outer  edges  by  the  distance-ring  N,  and  by  through-bolts  (Sec. 
CD).  The  copper  plates  already  referred  to  are  clamped  at  their 
outer  edges  between  the  sides  of  the  case  and  the  distance-ring  N. 
At  their  inner  edges  the  joint  is  made  by  means  of  wrought-iron 
rings,  secured  by  closely  spaced  machine-screws  tapped  into  the 
case.  The  copper  plates  are  thus  held  very  near  to  the  moving  disk, 
but  they  are  not  necessarily  in  absolute  contact  with  it.  Between 
the  copper  plates  and  the  sides  of  the  case  are  annular  spaces 
within  which  water  may  be  circulated.  It  will  be  seen  that  the 
case  with  its  copper  plates  is  quite  free  to  revolve  upon  the  hub 
of  the  cast-iron  disk ;  or  if,  as  in  practice,  the  case  is  at  rest,  the  disk 
may  revolve  freely  within  it.  It  will  be  seen,  also,  that  water  under 
pressure  in  the  annular  spaces  will  force  the  light  copper  plates 
against  the  moving  cast-iron  disk;  that,  as  a  result  of  this  contact, 
there  will  be  a  tendency  on  the  part  of  the  case  to  turn  with  the 
cast-iron  disk,  and  that  if  this  tendency  is  overcome  by  an  outside 
resistance,  power  will  be  absorbed.  This,  in  brief,  is  the  action  of 
the  brakes;  the  case,  in  the  present  instance,  is  prevented  from  turn- 
ing by  anchor-rods  connecting  it  with  the  foundation  (Fig.  10). 


LOCOMOTIVE  PERFORMANCE. 
± 


THE  DEVELOPMENT  OF  THE  PURDUE    TESTING-PLANT.   15 


The  circulating  water  enters  at  the  opening  Q  (Fig.  10),  passes 
from  the  annular  space  on  this  side  of  the  case  to  that  on  the  other 
side  by  eighteen  f-inch  holes  through  the  copper  plates  and  the 
distance-ring  (Sec.  EF),  and  is  finally  discharged  at  the  opening  R} 
sufficient  water  being  allowed  to  pass  to  carry  away  the  heat  result- 
ing from  the  friction.  To  prevent  the  water  pressure  within  the 
brake  from  spreading  the  sides  of  the  case,  the  rings  S  are  fitted 
over  a  feather  to  the  hub  of  the  moving  disk,  and  are  held  to  their 
place  by  nuts  which  screw  up  to  a  shoulder. 

When  the  brake  is  in  use,  all  clearance  space  between  the  cop- 
per plates  and  about  the  moving  cast-iron  disk  is  filled  with  oil. 
The  distribution  of  the  oil  is  secured  by  thirty-two  radial  grooves 
on  each  face  of  the  cast-iron  disk  (Fig.  10),  and  by  a  spiral  groove 


ARRANGEMENT 

FOR 
OIL.  CIRCULATION 


FIG.  11. 

extending  from  the  inner  edge  to  the  cirqumference  of  the  rubbing 
surfaces  of  the  disk,  with  a  pitch  of  about  4  inches.  The  entire 
rubbing  area  of  the  cast-iron  disk  is  thus  split  up  into  surfaces  the 
length  or  breadth  of  which  in  no  case  greatly  exceeds  4  inches.  The 
spiral  oilway  gives  these  surfaces  such  positions  that  in  passing  a 
given  point  on  the  copper  plate  they  continually  change  their  align- 
ment, which  fact,  it  is  believed,  greatly  assists  in  the  distribution  of 
the  oil.  The  radial  grooves  give  rise  to  a  slight  pumping  action, 
by  means  of  which  the  oil  may  be  kept  in  circulation  between  the 
center  and  circumference  of  the  brake.  Provision  for  this  circula- 
tion is  made  as  shown  by  Fig.  1 1 ;  the  oil  passes  the  valve  and  piping 
a  from  the  highest  point  in  the  brake,  is  received  by  the  filter-can. 


16  LOCOMOTIVE  PERFORMANCE 

and  is  thence  delivered  to  the  center  of  the  brake.  The  filter-can 
also  serves  the  purpose  of  a  supply  reservoir,  and  always  contains 
surplus  oil  when  the  brake  is  in  action.  This  circulation  helps  to 
maintain  the  oil  at  a  uniform  temperature,  subjects  all  parts  to  the 
same  service,  and  gives  a  ready  means  for  detecting  any  defect  which 
may  arise  in  the  lubrication  of  the  brake.  One  of  the  brakes  with 
one-half  of  the  case  removed,  exposing  one  of  the  rubbing  surfaces  of 
the  moving  disk,  is  shown  by  Fig.  2. 

As  preliminary  to  the  design  of  these  brakes,  the  load  which 
they  would  need  to  carry  was  determined  as  follows:  The  locomo- 
tive drivers  were  63  inches  in  diameter,  and 
the  sum  of  the  moments  about  the  two 
driving-axles  when  the  engine  was  exerting 
a  tractive  force  of  16,000  pounds  (assumed 

63 

to  be  maximum)  was  therefore  16,000 = 

42,000  foot-pounds,  which,  since  the  support- 
ing wheels  were  of  the  same  diameter  with 
the  drivers,  was  the  moment  under  which 
the  brakes  on  the  supporting  axles  must  work. 
Other  considerations  led  to  an  early  decision 

FlG'-  A.2'7TA  ?n1c,tioi}~b^ake  to  use  two  brakes  on  each  axle,  making  it  neces- 
with   One-half    of    Case 
Removed.  sary,  therefore,  for  each  brake  to  act  under  a 

maximum  moment  of  10,500  foot-pounds. 

Before  fixing  upon  the  dimensions  of  the  proposed  brakes,  a 
rather  extensive  series  of  experiments  was  made  upon  a  small  Alden 
brake  then  in  use  in  the  laboratory,  for  the  purpose  of  determining 
the  probable  value  of  the  coefficient  of  friction  which  would  attend 
the  action  of  such  a  brake.  These  preliminary  experiments  were 
made  on  a  21-inch  disk-brake  while  driven  at  speeds  varying  from 
300  to  450  revolutions  per  minute.  From  these  experiments  it 
appeared  that  lubrication  could  be  maintained  with  certainty  under 
a  water  pressure  of  40  pounds  per  square  inch,  and  this  pressure  was 
adopted  as  the  maximum  to  be  used  in  the  design  of  the  larger  brakes 
herein  described.  It  also  appeared  that  the  apparent  coefficient 
of  friction  *  varied  from  2.7%  to  over  4%,  depending  largely  on  the 

*  By  apparent  coefficient  of  friction  is  meant  that  factor  which  is  obtained  by 
assuming  that  the  entire  moment  of  the  brake  is  due  to  the  friction  between  the 
rubbing  surfaces  of  the  moving  disk  and  the  copper  plates.  Since  there  are  other 
rubbing  surfaces,  it  is  clear  that  the  apparent  coefficient  of  friction  is  larger  than 
the  actual  coefficient. 


THE  DEVELOPMENT  OF   THE  PURDUE    TESTING-PLANT.  17 

viscosity  of  the  oil  used  and  upon  the  temperature  of  the  brake. 
It  was  thought  that  3.5%  would  be  a  safe  coefficient  for  moderate 
speeds,  and  this  factor  was  accordingly  used. 

The  moment  in  foot-pounds  required  to  revolve  one  disk  upon 
another  against  the  action  of  friction,  when  the  two  are  bearing 
face  to  face,  is  the  product  of  the  area  in  contact,  the  pressure  of 
contact  per  unit  area,  the  coefficient  of  friction,  and  two-thirds  the 
radius  of  the  disk  in  feet.  Representing  this  statement  by  an  equa- 
tion, we  write 


., 

where    M  =  moment  of  force  in  foot-pounds; 
A  =  area  in  contact  in  square  inches 

-*»«; 

p  =  pressure  in  pounds  per  unit  area; 
/  =  the  coefficient  of  friction  ; 
r  =  the  radius  of  the  circular  plate  in  inches. 

But  each  brake  of  the  design  in  question  (Fig.  10)  consisted  of  a 
revolving  disk  with  a  fixed  copper  plate  on  either  side,  thus  giving 
two  rubbing  surfaces,  and  for  such  a  brake  the  moment  will  be 


(1) 


Again,  the  copper  plates  forming  the  rubbing  surfaces  were  not  com- 
plete disks,  but  rings.  The  moment  necessary  to  revolve  such  a 
disk  against  such  a  ring  will  be  the  same  as  the  moment  necessary 
to  revolve  a  disk  of  a  radius  equal  to  the  outer  radius  of  the  ring, 
less  the  moment  necessary  to  revolve  a  disk  of  a  radius  equal  to  the 
inner  radius  of  the  ring.  Now  if 

ri  =  the  outer  radius  of  the  ring  in  inches, 
7*2  =  the  inner  radius  of  the  ring  in  inches, 

we  may  write,  by  the  aid  of  equation  (1),  for  the  moment  of  the 
ring  in  foot-pounds, 


(2) 


18 


LOCOMOTIVE  PERFORMANCE. 


I 
"o 

3 

I 


THE  DEVELOPMENT  OF  THE  PURDUE   TESTING-PLANT.    19 

As  already  stated,  previous  experiments  with  a  trial  brake  had 
shown  that  a  coefficient  of  friction  of  0.035  could  be  depended  upon. 
The  maximum  water  pressure  assumed  for  the  design  was  40  pounds 
per  square  inch,  and  trial  solutions  which  were  carried  out  as  the 
design  was  in  process  of  development  made  r\  equal  to  28  inches 
and  T2  equal  to  10  inches.  Substituting  these  values  in  equation  (2) 
gives 

M  =  — -X40X0.035X  (21952-  1000)  =  10234, 

which  is  to  be  compared  with  the  required  moment  of  10,500  foot- 
pounds. It  is  evident  that  the  best  available  information  indicated 
that  the  dimensions  chosen  were  such  as  to  make  the  brakes  well 
suited  to  the  requirements  of  their  anticipated  service. 

7.  Traction  Dynamometer  is  shown  by  Fig.  13.  The  outline 
plan  and  elevation  in  this  figure  show  the  relative  position  of  the 
different  levers  when  in  place.  The  details  of  each  lever  are  shown 
by  the  remainder  of  the  plate. 

The  main  lever  A  being  first  referred  to,  the  following  description 
will  be  seen  to  apply.  This  lever  was  supported  by  a  round  steel 
pin  which  connected  it  with  the  cast  plate  E,  and  which  in  turn 
was  securely  bolted  to  the  heavy  timbers  which  formed  a  part  of 
the  framework  behind  the  locomotive.  The  round  rod  F  was  an 
extension  of  the  locomotive  draw-bar,  and  the  pull,  or  push,  of  the 
locomotive  was  exerted  along  the  line  of  its  axis.  Stress  was 
transmitted  from  this  rod  to  the  blocks  /  by  nuts  as  shown,  the  fit 
between  the  nuts  and  the  blocks  being  spherical  (detailed  view,  Fig. 
13)  to  allow  slight  changes  in  the  direction  of  F.  The  blocks  /  were 
connected  with  the  short  arm  of  the  lever  A  by  the  round  steel  pins 
g,  and  the  long  arm  of  this  lever  was  engaged  by  the  hook  I,  which 
was  free  to  move  within  the  link  k.  To  illustrate  the  action  of  this 
part  of  the  dynamometer,  let  it  now  be  assumed  that  the  pull  of 
the  locomotive  on  the  draw-bar  F  is  ahead,  that  is,  in  the  direction 
of  the  upper  arrow;  then  the  stress  on  the  draw-bar  will  result  in 
a  tendency  to  raise  the  hook  I,  and  the  lever  B  with  its  weight  will 
serve  only  as  a  counterbalance  to  the  lever  A.  But  if  it  be  assumed 
that  the  locomotive  is  working  aback,  that  is,  that  the  stress  in  the 
draw-bar  is  in  the  direction  of  the  lower  arrow,  the  long  arm  of  the 
lever  A  with  the  hook  /  will  tend  to  fall.  Motion  of  I  in  this  direc- 
tion, however,  is  soon  arrested  by  the  link  k,  which  by  virtue  of  its 


20  LOCOMOTIVE  PERFORMANCE. 

connection  with  the  lever  B  rises  as  I  falls,  until  it  engages  the  check- 
nuts  i]  these  are  thus  made  a  means  of  transmitting  the  stress  to 
the  hook  I,  which  as  before  will  move  upward,  while  the  shackle 
at  the  upper  end  of  the  hook  I  is  entirely  free  from  stress.  It  will 
thus  be  seen  that,  whether  the  locomotive  is  assumed  to  be  working 
in  forward  or  in  backward  gear,  its  tractive  force  is  made  manifest 
by  an  upward  movement  of  the  hook  Z,  from  which  point  two  simple 
levers  complete  the  dynamometer. 

The  direction  of  the  lever  C,  which  connected  with  hook  Z,  was  at 
right  angles  with  that  of  the  lever  A,  its  purpose  being  to  bring  the 
last  lever  D  of  the  system  out  from  behind  the  locomotive.  The 
lever  D  carried  a  weight-holder  arranged  to  receive  twenty  10-lb. 
weights.  The  ratio  of  the  whole  system  was  as  1  to  100;  each  weight, 
therefore,  that  was  balanced  at  the  weight-holder  represented  a 
tractive  force  exerted  by  the  locomotive  of  1,000  Ibs. 

A  small  dash-pot  (not  shown)  was  attached  to  the  last  lever,  D. 
The  lever  C  had  depending  from  it  a  light  rod,  which  controlled 
a  balanced  valve  B  (Figs.  6  and  7)  in  the  pipes  upplying  the  brakes 
with  water.  By  means  of  this  valve,  as  previously  described,  the 
load  on  the  brakes  was  made  to  vary  automatically  with  the  position 
of  the  last  lever  of  the  dynamometer. 

The  locomotive  while  in  motion  could  be  given  a  final  adjust- 
ment to  its  place  on  the  supporting  wheels  by  means  of  the  nuts  on 
the  draw-bar. 

Having  now  examined  the  more  important  principles  underlying 
the  design  of  the  first  plant,  we  may  make  inquiry  concerning  its 
behavior  in  service. 

8.  Behavior  of  the  Mounting  Mechanism  of  the  First  Plant. — 
Any  considerable  arrangement  of  machinery  which  is  new  in  the 
details  of  its  design,  or  which  is  required  to  serve  purposes  which 
are  new,  must  for  a  time  be  considered  experimental.  The  mounting 
mechanism  of  the  locomotive  testing-plant  was  novel  in  many  of 
its  details,  and  the  conditions  surrounding  its  use  were  new.  Each 
element  entering  into  the  make-up  of  the  plant,  therefore,  demanded 
in  its  turn  its  full  share  of  patiently-bestowed  and  long-continued 
attention.  The  most  important  element  was  the  friction-brakes 
by  which  the  power  of  the  locomotive  upon  the  mount  was  absorbed. 
These,  as  already  stated,  had  been  designed  upon  a  principle  which  had 
been  previously  developed  by  Professor  Alden,  but  no  brakes  had 
before  been  made  approaching  in  capacity  those  of  the  Purdue  plant. 


THE  DEVELOPMENT  OF    THE  PURDUE    TESTING-PLANT.  21 

Their  ability  to  perform  the  work  for  which  they  were  intended  was 
early  settled  beyond  question.  When  they  were  first  used,  the  oil 
became  very  hot  about  the  outside  of  the  case,  while  that  in  other 
parts  of  the  apparatus  remained  cool.  To  avoid  this  accumulation 
of  heat  around  the  outside  of  the  case,  closed  circulating  pipes  were 
added  to  convey  the  hot  oil  from  the  outer  portions  of  the  case  back 
to  the  center,  the  radial  curves  in  the  disks  being  sufficient  to 
maintain  a  pumping  action  by  which  there  was  a  continuous  flow 
of  oil  from  the  outside  to  the  center  of  the  brake.  These  pipes  took 
the  place  of  the  open  circulation  provided  for  in  the  original  design. 
They  served,  also,  to  maintain  all  portions  of  the  brake  at  an  approxi- 
mately uniform  temperature,  the  excess  of  heat  being  carried  away 
by  the  circulating  water  as  already  described.  The  brakes  were 
lubricated  by  a  cheap  grade  of  cylinder-oil,  which  was  supplied  by 
the  cans  shown  by  Fig.  11.  There  was  always  some  leakage  at  the 
center,  but  no  more  than  was  desirable  to  insure  lubrication  of  that 
point.  The  drip  was  caught  and  returned  to  the  can. 

In  the  original  design  of  the  brakes  it  was  assumed  that  the  work 
absorbed  would  be  proportional  to  the  water  pressure  exerted  upon 
the  copper  plates,  an  assumption  which  would  be  true  provided  the 
lubricant  between  the  copper  plates  and  the  cast-iron  moving  disk 
was  always  in  the  same  condition.  In  practice  it  appears  that  the 
work  is  all  done  on  the  oil  and  any  change  of  condition  resulting 
in  a  change  in  the  amount  of  work  absorbed  produces  a  correspond- 
ing effect  upon  the  temperature  and,  hence,  upon  the  viscosity  of 
the  oil.  Other  things  being  equal,  therefore,  increasing  or  diminish- 
ing the  pressure  does  not  result  in  a  proportional  increase  or  dimi- 
nution of  the  amount  of  work  absorbed.  The  effect  of  this  obser- 
vation is  expressed  by  saying  that  the  amount  of  work  absorbed 
by  the  brakes  depends  quite  as  much  upon  the  temperature  of  the 
oil  in  the  brakes  as  upon  the  pressure  exerted  between  the  copper 
plate  and  the  moving  disk;  and  in  practice,  excepting  when  the 
speed  of  revolution  is  very  small,  it  is  found  best  to  use  a  moderate 
water  pressure,  and  to  vary  the  load  by  varying  the  brake  tempera- 
ture, this  being  easily  accomplished  by  controlling  the  amount  of 
circulating  water.  The  water  pressure  under  ordinary  conditions  of 
service  rarely  exceeds  10  pounds. 

It  has  been  stated  that  the  work  absorbed  by  the  brakes  is  prac- 
tically limited  to  that  which  is  represented  by  the  force  necessary 
to  overcome  the  viscosity  of  the  oil.  Evidence  of  the  truth  of  this 


22 


LOCOMOTIVE  PERFORMANCE. 


statement  is  to  be  found  in  the  fact  that  the  bearing  pressure  between 
the  copper  plate  and  the  moving  disk,  being  seldom  over  10  pounds 
per  square  inch,  causes  no  perceptible  wear  of  the  rubbing  surfaces 
so  long  as  lubrication  is  maintained.  The  copper  plates  and  the 
cast-iron  disk  which  constitute  the  rubbing  surfaces  of  the  four  brakes, 
after  a  total  of  six  million  revolutions  show  wear  in  only  in  spots 
on  the  copper  plates  where,  owing  to  imperfections  in  the  surface, 
small  areas  have  received  a  concentration  of  pressure.  Since  the 
work  absorbed  by  the  brakes  depends  largely  upon  the  temperature  of 
the  oil  which  lubricates  their  rubbing  surfaces,  it  will  appear  that  the 


FIG.  14. — The  Dynamometer,  Mechanism  for  Controlling  Pressure  on  Brakes, 
and  the  Revolution  Counters.     First  Plant    1891. 

maximum  load  will  be  greatest  when  the  heat  developed  between  the 
rubbing  surfaces  is  most  quickly  conducted  away.  The  copper 
plates  in  the  brakes  under  consideration  were  made  -&  of  an  inch 
in  thickness.  It  is  probable  that  less  cooling  water  would  be  required 
and  the  action  of  the  brakes  would  be  improved  if  the  thickness  of 
these  plates  were  considerably  reduced.  They  can  perhaps  be  reduced 
until  only  a  sufficient  amount  of  metal  remains  to  withstand  the 
shearing  forces  to  which  the  action  of  the  brake  subjects  them. 

The  dynamometer  to  which  the  draw-bar  of  the  engine  was  con- 
nected (Fig.  13),  while  reasonably  satisfactory,  was  not  well  cal- 
culated to  absorb  the  heavy  vibrations  which  at  high  speed  the  loco- 
motive brought  upon  it.  The  structure  behind  the  locomotive  was 


cr  THF  ^\ 

UN1VERSITY 


THE  DEVELOPMENT   OF    THE  PURDUE   TESTING-PLANT.  23 

several  times  strengthened.  First,  the  woodwork  upon  which  the 
dynamometer  was  mounted  was  reenforced,  the  anchorage  behind 
it  increased,  and  a  small  dash-pot  added  to  its  last  lever.  Later  a 
larger  dash-pot  having  a  diameter  of  12  inches  was  interposed 
between  the  fixed  tender-frame  behind  the  locomotive  and  a  bracket 
attached  to  the  locomotive  foot-plate.  This,  being  entirely  indepen- 
dent of  the  dynamometer,  served  to  absorb  the  larger  part  of  the 
vibrating  forces  incident  to  high  speed,  and  after  its  addition  no 
difficulty  was  experienced  either  in  holding  the  engine  or  in  measuring 
approximately  its  pull.  The  dynamometer  was  not,  however,  a  piece 
of  apparatus  whose  accuracy  could  be  relied  upon  under  all  condi- 
tions of  service. 

In  view  of  the  enormous  force  which  a  locomotive  is  capable 
of  exerting  it  would  appear,  at  first  sight,  that  an  error  of  50  or  even 
100  pounds  in  the  determination  of  draw-bar  stresses  would  be  of 
slight  consequence,  and  that  great  accuracy  in  this  matter  would  not 
be  required.  Under  some  conditions  this  conclusion  is  correct,  but 
under  others  it  is  far  from  true.  The  work  done  at  the  draw-bar 
is  the  product  of  the  force  exerted  multiplied  by  the  space  passed 
over.  If  the  force  exerted  is  great  and  the  speed  low,  a  small  error 
in  the  draw-bar  stress  is  not  a  matter  of  great  importance,  but  if 
the  reverse  conditions  exist  —  if  the  force  is  small  and  the  speed 
is  high  —  then  it  is  absolutely  necessary  that  the  draw-bar  stresses 
be  determined  with  great  accuracy.  Moreover,  high  speeds  necessarily 
involve  low  draw-bar  stresses.  A  locomotive  which  at  ten  miles 
an  hour  may  pull  12,000  pounds  will  have  difficulty,  when  running 
at  sixty  miles  an  hour,  in  maintaining  a  pull  of  2,500  pounds.  When, 
therefore,  in  the  general  progress  of  events,  the  opportunity  came 
to  improve  the  character  of  the  dynamometer,  considerations  such 
as  have  been  stated  were  deemed  of  sufficient  importance  to  justify 
the  purchase  of  the  most  accurate  apparatus  which  could  be  found. 

The  exhaust-fan  over  the  engine  (Fig.  8)  was  a  detail  made 
necessary  by  the  character  of  the  room  in  which  the  locomotive 
was  located  and  the  variety  of  equipment  by  which  it  was  surrounded. 
It  never  failed  to  serve  its  purpose,  and  when  steam  was  being  raised 
it  was  invaluable. 

A  minor  difficulty  encountered  in  the  course  of  the  early  work 
upon  the  plant  was  that  due  to  the  tendency  of  oil  used  upon  the 
bearings  of  the  supporting  axles  to  follow  the  arms  of  the  supporting 
wheels  out  to  the  rim  and  thence  to  reach  the  locomotive  drivers. 


24  LOCOMOTIVE  PERFORMANCE. 

This  oil  by  spreading  over  the  faces  of  the  supporting  wheels  and 
drivers  reduced  adhesion  and  greatly  interfered  with  the  action 
of  the  plant.  A  remedy  was  found  in  the  attachment  of  a  ring  to 
the  face  of  the  supporting-wheel  hub  of  such  form  as  would  receive 
and  retain  by  centrifugal  force  all  drip  occurring  during  a  run.  Still 
other  minor  changes  will  be  found  worked  out  as  accomplished  facts 
in  Purdue's  second  plant,  a  description  of  which  is  to  follow. 


FIG.  15. — The  Engineering  Laboratory,  Purdue  University,  prior  to  Jan.  23,  1  94. 

9.  The  Work  of  the  First  Plant. — During  the  school  year  of 
1891-2,  following  the  installation  of  the  plant,  work  upon  it  was 
directed  more  to  the  perfection  of  mechanical  features  than  to  the 
acquistion  of  scientific  data.  Nevertheless,  during  this  year  twenty 
efficiency  tests  were  run,  many  of  them  at  light  power  and  almost 
all  with  the  throttle  only  partially  open,  and  later  an  experimental 
investigation  concerning  the  action  of  the  counterbalance  was  under- 
taken. 

It  was  not  until  the  fall  of  1893  that  the  plant  was  in  such  com- 
plete working  order  that  tests  at  high  power  could  be  run  with  cer- 
tainty. During  the  latter  part  of  this  year,  however,  a  consider- 
able number  of  such  tests  were  carried  out  and  much  was  expected 
from  an  early  study  of  the  results,  but  no  essential  fact  was  ever 
established  from  these  data.  On  January  23,  1894,  the  Engineering 
Laboratory,  which  by  a  succession  of  additions  had  increased  greatly 
in  size,  was  burned.  All  experimental  data  which  had  not  been 
published  were  lost,  and  the  locomotive  went  down  in  the  wreck. 
The  fire  entailed  a  heavy  burden  of  labor  and  expense.  Tut  with 


THE  DEVELOPMENT  OF  THE  PURDUE  TESTING-PLANT.   25 

the  new  responsibilities  which  it  brought  there  came  also  new  oppor- 
tunities. All  details  of  the  mounting  mechanism  were  most  care- 
fully reviewed,  and  every  fragment  of  experience  was  made  to  serve 
a  useful  purpose  in  the  design  of  a  new  plant.  A  permanent  track 
8,000  feet  in  length  was  laid  to  connect  the  laboratory  with  the  rail- 
ways of  the  country.  The  damaged  locomotive  was  extricated  from 
the  ruin,  sent  out  over  the  track  and  thence  to  Indianapolis  for  repairs. 
Upon  its  return  a  few  weeks  later,  it  was  put  under  its  own  steam 
and  backed  in  over  the  Purdue  track  directly  to  its  place  upon  the 
supporting  wheels  of  a  new  testing-plant.  The  ease  and  rapidity 


FIG.  16. — The  LocDmative-testing  Plant  Immediately  after  the  Fire. 

with  which  this  trip  was  made  were  in  striking  contrast  with  the 
laborious  methods  which  attended  its  first  trip  across  the  same  terri- 
tory. Four  months  after  the  fire  the  new  work  had  been  completed 
and  the  reconstructed  engine  was  in  position. 

10.  The  Second  Testing-plant. — The  new  plant,   as  shown  by 
the  accompanying  plates,  occupies  a  building  especially  planned  to 
receive  it,  and  is  arranged  for  the  accommodation  of  any  locomotive. 
The  dotted  outline  in  Fig.  17  is  to  the  scale  of  the  University's  loco- 
motive Schenectady. 

11.  The  New  Wheel  Foundation. — By  reference  to  Figs.  17  and 
18  it  will  be  seen  that  there  is  provided  a  wheel  foundation  of  nearly 
twenty-five  feet  in  length.     This  is  more  than  sufficient  to  include 
the  driving-wheel  base  of  any  standard  eight-,  ten-,  or  twelve-wheeled 


26 


LOCOMOTIVE  PERFORMANCE. 


THE  DEVELOPMENT  OF   THE  PURDUE   TESTING-PLANT.  27 

engine.  For  engines  having  six  wheels  coupled,  a  third  supporting 
axle  will  be  added  to  those  shown,  and  for  engines  having  eight 
wheels  coupled  four  new  axles,  having  wheels  of  smaller  diameter 
than  those  shown,  will  be  used. 

The  wheel  foundation  carries  cast-iron  bed-plates,  to  which  are 
secured  pedestals  for  the  support  of  the  axle-boxes.  The  lower 
flanges  of  the  pedestals  are  slotted  and  the  bed-plates  have  threaded 
holes  spaced  along  their  length.  By  these  means  the  pedestals  may 
be  adjusted  to  any  position  along  the  length  of  the  foundation. 

The  boxes  in  use  at  present  are  plain,  babbitted  shaft-bearings, 
and  between  each  bearing  and  its  pedestal  a  wooden  cushion  is  inserted. 
A  bearing  has  been  designed,  for  use  in  some  special  experiments 
which  provides  for  the  suspension  of  the  axle  from  the  springs,  but 
has  not  yet  been  used. 

The  outer  edges  of  the  wheel  foundations  are  topped  by  tim- 
bers to  which  the  brake-cases  are  anchored.  The  brakes  which 
absorb  the  power  of  the  engine  are  those  which  were  used  in  the 
original  plant,  and  which  have  been  described.  The  fire  caused 
no  serious  damage  to  this  portion  of  the  apparatus. 

12.  The  Emery  Dynamometer. — The  vibrating  character  of  the 
stresses  to  be  measured  makes  the  design  of  the  traction  dynamom- 
eter a  matter  of  some  difficulty.  The  dynamometer  of  the  original 
plant  consisted  of  an  inexpensive  system  of  levers  attached  to  a 
heavy  framework  of  wood,  the  vibrations  being  controlled  by  dash- 
pots.  In  the  present  construction  wood  as  a  support  is  entirely 
abandoned  and  a  massive  brick  pier,  well  stayed  with  iron  rods, 
has  been  substituted.  The  dynamometer  connects  with  the  draw- 
bar at  the  rear  of  the  locomotive.  It  consists  of  the  weighing-head 
of  an  Emery  testing-machine,  the  hydraulic  support  of  which  is  capa- 
ble not  only  of  transmitting  the  stress  it  receives,  but  also  of  with- 
standing the  rapid  vibrations  which  the  draw-bar  transmits  to  it. 
The  apparatus  is  of  30,000  pounds  capacity,  and  at  the  same  time  is 
so  sensitive  that  one  standing  in  front  of  the  locomotive  may  press 
with  his  fingers  upon  its  pilot  and  cause  a  deflection  of  the  needle 
of  the  dynamometer. 

As  is  well  known,  the  arrangement  of  the  hydraulic  support  of 
the  Emery  testing-machine  permits  the  weighing-scale  to  be  at  any 
convenient  distance  from  the  point  where  the  stresses  are  received. 
Figs.  17  and  18  show  only  the  receiving  end  of  the  apparatus.  The 
draw-bar  connects  with  this  apparatus  by  a  ball-joint,  which  leaves 


28 


LOCOMO  Tl  VE  PERFORMANCE. 


I 


I 

1 

1 


THE  DEVELOPMENT  OF  THE  PURDUE  TESTING-PLANT.  31 

its  outer  end  free  to  respond  to  the  movement  of  the  locomotive 
on  its  springs.  A  threaded  sleeve  allows  the  draw-bar  to  be  lengthened 
or  shortened  for  a  final  adjustment  of  the  locomotive  to  its  position 
upon  the  supporting  wheels;  and,  finally,  to  meet  the  proportions 
of  different  locomotives,  provision  is  made  for  a  vertical  adjust- 
ment of  the  entire  head  of  the  machine  upon  its  frame. 

13.  The  Superstructure. — Figs.  20  and  21  show  the  arrangement 
of  floors.     The  "visitors'  floor"  (Fig.  21)  and  the  fixed  floors  adjoin 
ing  are  at  the  level  of  the  rail.     The  open  space  over  the  wheel  foun- 
dation is  of  such  dimensions  as  will  easily  accommodate  an  engine 
having  a  long  driving-wheel  base,  movable  or  temporary  floors  being 
used  to  fill  in  about  each  different  engine,  as  may  be  found  convenient. 
The  temporary  flooring  shown  is  that  employed  for  the  Purdue  loco- 
motive. 

The  level  of  the  " tender  floor"  is  at  a  sufficient  height  above 
the  rail  to  serve  as  a  platform  from  which  to  fire.  At  the  rear  is  a 
runway  leading  to  the  coal-room,  the  floor  of  which  is  somewhat  lower 
than  the  tender  floor.  A  platform  scale  is  set  flush  with  the  floor  at 
the  head  of  the  runway.  During  tests  the  scale  is  used  for  weigh- 
ing the  coal  which  is  delivered  to  the  fireman. 

The  feed-water  tank,  from  which  the  injectors  draw  their  supply, 
is  shown  in  the  lower  right-hand  corner  of  Fig.  21.  Above  this 
supply-tank  are  two  small  calibrated  tanks  so  arranged  that  one 
may  be  filled  while  the  other  is  discharging. 

The  steam-pump  shown  on  the  visitors'  floor  is  for  the  purpose 
of  supplying  water  under  pressure  to  the  friction-brakes  which  load 
the  engine. 

The  conditions  under  which  the  engine  is  operated  are  at  all 
times  within  the  control  of  a  single  person,  whose  place  is  just  at 
the  right  of  the  steps  leading  to  the  tender  floor.  From  this  posi- 
tion he  can  see  the  throttle  and  reverse-lever  and  observe  all  that 
goes  on  in  the  cab.  At  his  right  is  the  dynamometer  scale-case, 
wherein  is  shown  the  load  at  the  draw-bar;  in  front  are  the  gauges 
giving  the  water  pressure  on  the  brakes;  and  under  his  hand  are 
the  valves  controlling  the  circulation  of  water  through  the  brakes. 

No  attempt  has  been  made  in  these  drawings  to  show  small  acces- 
sory apparatus,  neither  does  it  seem  necessary  to  give  an  enumera- 
tion. 

14,  The  Building. — Fig.  23  presents  several  views  of  the  loco- 
motive building.     The  entrance-door,  which   opens  upon  the  visi- 


LOCOMOTIVE  PERFORMANCE. 


34  LOCOMOTIVE  PERFORMANCE. 

tors'  floor,  is  shown  in  the  south  elevation.  It  is  approached  from 
the  general  laboratory,  150  feet  away. 

The  north  and  west  elevations  show  the  roof  construction  by 
which  the  upper  end  of  the  locomotive  stack  is  made  to  stand  out- 
side of  the  building.  The  roof  sections  shown  may  be  entirely  removed, 
and  a  door  in  the  cross-wall,  which  extends  between  the  removable 
roof  and  the  main  roof,  provides  ample  height  for  the  admission 
of  the  locomotive  to  the  building.  A  window  in  this  door  (Fig.  20) 
serves  to  give  the  fireman  a  clear  view  of  the  top  of  the  locomotive 
stack  from  his  place  in  the  cab,  a  condition  which  is  essential  to 
good  work  in  firing.  Above  the  stack  is  a  pipe  to  convey  the  smoke 
clear  of  the  building.  To  meet  a  change  in  the  location  of  the  stack 
this  pipe  may  be  removed  to  any  position  along  the  length  of  the 
removable  roof.  An  illustration  from  a  photograph  of  the  interior, 
taken  when  the  plant  was  in  operation,  is  given  as  Fig.  22. 

In  connection  with  the  plan  of  the  building  (Fig.  23)  there  is  shown 
the  arrangement  of  tracks  for  the  locomotive  and  of  those  used  for 
supplying  coal.  Fig.  24  is  an  exterior  view  of  the  locomotive  labora- 
tory when  the  plant  is  working,  and  Fig.  25  gives  the  position  of 
the  locomotive  or  annex  laboratory,  relative  to  the  whole  group 
of  buildings  of  which  it  forms  a  part. 

15.  Work  with  the  New  Plant  began  in  the  fall  of  1894  and  con- 
tinued without  interruption  for  more  than  two  years.  In  the  course 
of  this  time  most  of  the  results  were  secured  which  are  to  be  dis- 
cussed in  the  succeeding  chapters.  Fifty  or  more  efficiency  tests 
of  boiler  and  engine,  under  various  conditions  of  speed,  load,  cut-off, 
steam  pressure,  and  valve  proportion,  were  run.  A  large  amount 
of  time  was  spent  in  determining  the  amount  of  work  lost  in  machinery 
friction  under  different  conditions  of  running.  A  study  was  made 
of  the  effect  of  high  rates  of  combustion  upon  boiler  efficiency,  of 
the  conditions  affecting  the  draft  action  produced  by  the  exhaust, 
of  steam  distribution  by  plain  and  Allan-ported  valves,  and  of  the 
power  necessary  to  move  balanced  and  unbalanced  valves. 

In  the  course  of  this  work,  and  of  that  done  upon  the  first  plant, 
not  less  than  10,000  indicator-cards  were  taken,  20,000  miles  were 
run,  and  25,000  different  observations  made.  From  these  data  about 
12,000  derived  results  had  been  obtained,  making  a  total  of  nearly 
50,000  facts  which  were  then  available  to  disclose  the  performance 
of  this  experimental  locomotive.  It  is  perhaps  safe  to  say  that 
there  was  nowhere  such  an  accumulation  of  locomotive  data  obtained 


THE  DEVELOPMENT  OF   THE  PURDUE  TESTING-PLANT    37 


LOCOMOTIVE  PERFORMANCE. 


FIG.  24.— The  Locomotive  Laboratory,  1894. 


LOCOMOTIVE    I    COAL    0 

LABORATORY     | 


WOOD  ROOM        ENGINEERING  LABORATORYU     MACHINE  ROOM 

LOCKERS  !  II  LOCKERS 


FIG.  25. — A  Plan  of   the   Reconstructed   Engineering  Laboratory,  Purdue 

University,  1898. 


THE  DEVELOPMENT  OF   THE  PURDUE  TESTING-PLANT.  39 

under  conditions  so  favorable  to  experimentation,  and  arranged 
so  systematically,  as  the  material  then  existing  in  the  Purdue 
laboratory. 


FIG.  26.— The  Departure  of  Schenectady  No.  1, 


FIG.  27. — Schenectady  No.  1  in  a  New  Role. 

16.  Sale  of  Locomotive  "  Schenectady." — The  six  years  which  fol- 
lowed the  introduction  of  Schenectady  into  the  Purdue  laboratory 


40  LOCOMOTIVE  PERFORMANCE. 

had  been  marked  by  unusual  progress  in  locomotive  design,  and 
by  the  end  of  that  period  the  experimental  engine  had  ceased  to 
Le  representative  of  the  most  approved  practice.  For  example, 
steam  pressures  of  180  or  200  pounds  per  square  inch  were  then 
common,  while  the  boiler  of  Schenectady  had  been  designed  for  a 
maximum  pressure  of  140  pounds.  Early  in  1897,  therefore,  it 
was  decided  that  locomotive  Schenectady  should  be  disposed  of 
and  another  engine  which  would  better  serve  the  purposes  of  the 


FIG.  28. — The  Second  Experimental  Locomotive  Schenectady  No.  2,  1897. 

laboratory  secured  to  take  its  place.  It  thus  happened  that  on  a 
bright  morning  in  May,  1897,  Schenectady,  hereafter  to  be  known 
as  Schenectady  No.  1,  steamed  out  of  its  "  rectangular  round-house  " 
and  slowly  made  its  way  across  the  campus  under  the  escort  of  a 
throng  of  students.  At  the  Art  Hall  a  stop  was  made  and  the  sig- 
nificance of  the  event  was  emphasized  by  brief  addresses.* 

Passing  from  Purdue's  possession,  Schenectady  became  the' 
property  of  the  Schenectady  Locomotive  Works,  and  later  entered 
regular  service  on  the  Michigan  Central  Railway.  Our  last  glimpse 

*  The  speakers  were  President  Smart,  Colonel  H.  G.  Prout,  and  two  members 
of  the  faculty. 


THE  DEVELOPMENT  OF  THE  PURDUE  TESTING-PLANT.  41 

of  the  machine  shows  it  at  the  head  of  a  train  on  this  road,  where 
its  identity  is  established  by  its  number,  422.* 

17.  Schenectady  No.  2  arrived  at  the  laboratory,  fresh  from 
its  builder's  hands,  in  October,  1897,  and  entered  at  once  upon  the 
work  for  which  it  was  designed.  Since,  however,  the  greater  part 
of  -the  data  discussed  in  succeeding  chapters  is  the  result  of  the 
work  done  on  Schenectady  No.  1,  a  description  of  Schenectady  No.  2 
wiU  for  the  present  be  omitted. 

*  The  photograph  from  which  Fig.  27  has  been  made  was  obtained  through 
the  courtesy  of  the  late  Mr.  Robert  Miller,  Superintendent  of  Motive  Power  and 
Equipment  of  the  Michigan  Central  Railway.  In  transmitting  the  photograph 
Mr.  Miller  wrote,  under  date  of  Dec.  11,  1897:  *' I  take  pleasure  in  forwarding  you 
to-day  ...  a  photograph  of  our  engine,  No.  422,  known  to  us  as  the  Purdue 
Locomotive.  Our  men  call  her  'the  schoolmarm. '  " 


CHAPTER  II. 

* 

GROWTH    OF   INTEREST    IN    LABORATORY    TESTS    OF    LOCOMOTIVES. 

18.  Locomotive  Operation  under  Conditions  other  than  those 
of  the  Track. — A  testing-plant  was  not  required  to  demonstrate  the 
practicability  of  operating  a  locomotive  with  the  machine  as  a  whole 
at  rest,  for,  previous  to  the  existence  of  such  a  plant,  locomo- 
tives had  been  made  to  serve  the  purposes  of  stationary  engines 
by  being  blocked  up  until  their  drivers  cleared  the  rails  enough  to 
carry  belts;  *  and  before  the  days  of  the  injector  it  sometimes  hap- 
pened that  an  engine  held  for  an  unusual  period  on  a  siding  was 
in  an  emergency  pumped  without  changing  its  position.  This  was 
accomplished  by  setting  a  jack  under  the  rear  of  the  engine  in  such 
a  manner  as  to  take  a  considerable  portion  of  the  weight  of  the  engine 
from  the  drivers,  which,  thus  relieved  of  pressure  and  aided  by  the 
application  of  oil  to  the  rail,  could  be  slipped  at  moderate  speed 
through  the  action  of  its  cylinder  while  the  pumps  delivered  feed- 
water  to  the  boiler.  Nor  has  the  student  of  locomotive  perform- 
ance failed  to  take  advantage  of  such  possibilities  as  these.  Thus, 
the  late  Alexander  Borodin,  when  Engineer-in-Chief  of  the  Russian 
Southwestern  Railway,  presented  the  results  of  an  elaborate  series 
of  tests  made  upon  a  small  locomotive  blocked  clear  of  the  track, 
with  belts  applied  to  the  drivers  in  such  a  way  that  the  power  developed 
could  be  absorbed  in  driving  shop  machinery,  f  But  in  neither  of 
these  cases  was  it  possible  to  operate  the  locomotive  under  con- 
ditions normal  to  the  track.  The  Purdue  plant  was  the  first  to 
receive  a  normal  engine  in  the  condition  in  which  it  might  be  as  it 

*  A  locomotive  thus  arranged  was  seen  driving  the  machinery  of  a  railway  repair- 
shop  in  Montgomery,  Ala.,  in  the  winter  of  1866. 

t  "Experiments  on  the  Steam- jacketing  and  Compounding  of  Locomotives  in 
Russia,''  by  Alexander  Borodin,  Mem.  Inst.  M.  E.  Proceedings  of  the  Meetings  of 
the  Institution  of  Mechanical  Engineers,  London,  August,  1886. 

42 


GROWTH  OF  INTEREST  IN  LABORATORY   TESTS.  43 

came  from  the  road,  and  to  allow  such  an  engine  to  be  loaded  and 
run  in  a  perfectly  normal  way.* 

19.  Growth  of  Interest  in  Locomotive-testing. — The  year  1891, 
which  marked  the  installation  of  the  Purdue  locomotive  testing- 
plant,  and  those  immediately  succeeding,  represent  a  period  of  unu- 
sual interest  in  locomotive  design  and  performance.  The  preceding 
twenty-five  years  had  witnessed  the  development  of  the  vast  rail- 
way systems  of  this  country,  new  engines  had  been  constantly  in 
demand  for  the  operation  of  new  track,  and  shop  facilities  for  repair- 
ing them  were  required  to  be  constantly  increased.  When  there 
was  an  end  to  the  period  of  enormous  track  extension,  the  condi- 
tions affecting  locomotive  development  became  more  settled;  rail- 
way managers  began  to  enforce  economy  in  operation,  and  attention 
was  thus  turned  from  matters  of  construction  to  questions  of  per- 
formance. As  a  consequence,  much  activity  was  developed  in  test- 
ing locomotives  while  in  operation  on  the  road,  but  there  was  no 
standard  method  of  making  such  tests;  and  as  each  investigator  fol- 
lowed his  own  method,  a  comparison  of  results  proved  to  be  of  little 
value.  These  conditions  led  naturally  to  a  desire  for  greater  uni- 
formity in  practice,  which,  in  the  spring  of  1890,  found  expression 
at  a  meeting  of  the  American  Society  of  Mechanical  Engineers,  which 
resolved  "That  a  Committee  of  Seven  be  appointed  by  the  Chair 
to  report  on  Standard  Methods  of  Conducting  Tests  of  Efficiency 
of  Locomotives,  including  the  engine,  the  boiler,  the  quality  of  the 
steam,  and  the  comparative  efficiencies  of  simple  and  compound 
locomotives."  f 

The  debate  upon  the  resolution  there  adopted  revealed  the  limited 
and  indefinite  character  of  the  information  available  concerning  the 
performance  of  locomotives,  and  gave  expression  to  a  desire  for  fuller 
knowledge  upon  the  subject. 

In  the  early  summer  of  the  following  year  it  happened  that  the 
American  Society  of  Mechanical  Engineers  and  the  American  Rail- 
way Master  Mechanics'  Association  met  during  the  same  week  (June, 

*  In  this  connection,  it  will  be  well  to  note  that  in  the  course  of  a  discussion 
before  the  American  Society  of  Mechanical  Engineers  in  May,  1890  (Proceedings  of 
the  Society,  Vol.  XI,  p.  886),  Mr.  Louis  S.  Wright  proposed  a  scheme  for  testing 
locomotives  embracing  many  of  the  important  features  which  appear  in  the  Purdue 
plant,  as  designed  a  few  months  later,  and  it  is  probable  that  the  importance  of  the 
problem  had  led  others  to  consider  it  as  a  subject  for  speculation.  It  is  but  proper 
to  add  that  the  Purdue  designer  did  not  draw  his  inspiration  from  any  such  suggestion. 

f  Proceedings  of  the  American  Society  of  Mechanical  Engineers,  1890,  p.  591. 


44  LOCOMOTIVE  PERFORMANCE. 

1891),  one  at  Providence,  R.  I.,  and  the  other  at  Cape  May,  and  it 
happened  also  that  the  subject  of  locomotive  testing  was  introduced 
in  both  conventions.  The  Mechanical  Engineers  received  a  report 
of  progress  *  from  its  committee  appointed  a  year  previous,  and  the 
Master  Mechanics  appointed  a  committee  "to  investigate  the  prac- 
ticability of  establishing  a  standard  system  of  tests  to  demonstrate 
the  fuel  and  water  consumption  of  locomotives^  also  to  ascertain 
the  value  of  the  steam-engine  indicator  for  locomotive  use."f  In 
the  succeeding  year  (June,  1891,  to  June,  1892)  the  Mechanical 
Engineers'  Committee  made  no  report,  but  in  December,  1892,  it 
.again  reported  progress.  J  During  this  interval  the  Master  Mechanics7 
-Committee  had  asked  and  received  authority  to  confer  with  the 
'Committee  of  the  Mechanical  Engineers,  but  the  official  records  show 
:no  further  reference  to  the  work  of  either  committee  or  to  any  joint 
"work  done  by  them  until  the  summer  of  1893,  when  the  Committee 
of  trie  Master  Mechanics'  Association  presented  their  report  after 
conference  with  a  similar  committee  appointed  by  the  American 
Society  of  Mechanical  Engineers. §  The  report  gave  in  elaborate 
form  the  specifications  to  be  observed  in  conducting  tests  of  loco- 
motives upon  the  road.  It  is  an  interesting  fact  that  up  to  this 
time  the  record  contains  no  reference  to  laboratory  tests  or  to  loco- 
motive-testing plants. 

20.  Interest  in  Purdue's  Work. — A  paper  describing  Purdue's 
locomotive-testing  plant  was  presented  at  the  San  Francisco  meet- 
•ing  of  the  American  Society  of  Mechanical  Engineers  in  the  summer 
of  1892,||  where  it  failed  to  draw  out  any  discussion.  But  a  year 
later,  when  the  Master  Mechanics'  Committee  already  referred  to 
rendered  its  report,  the  Convention  after  due  discussion  resolved, 
first,  "That  the  Committee  on  Locomotive  Tests  be  instructed  to 
cooperate  with  the  Committee  from  the  Mechanical  Engineers'  Society 
in  a  series  of  comparative  shop  tests  of  compound  and  simple  loco- 
motives to  be  made  on  the  locomotive- testing  apparatus  of  Purdue 
University,"  and,  second,  "That  the  Executive  Committee  be  instructed 

*  Proceedings  of  the  American  Society  of  Mechanical  Engineers,   1891,  p.  613. 

f  The  committee  appointed  in  response  to  this  resolution  consisted  of  J.  N. 
lander,  J.  Davis  Barnett,  Albert  Griggs,  John  D.  Campbell  and  F.  W.  Dean.  (Pro- 
ceedings of  the  American  Railway  Master  Mechanics'  Association,  1891,  p.  206.) 

J  Proceedings  of  the  Society,  1893,  p.  21. 

§  Proceedings  of  the  American  Railway  Master  Mechanics'  Association,  1893,  p.  22. 

||  "An  Experimental  Locomotive."  Transactions  of  the  American  Society  of 
Mechanical  Engineers,  Vol.  XIII,  p.  427. 


GROWTH  OF  INTEREST  IN  LABORATORY   TESTS.  45 

to  provide  funds  to  pay  the  necessary  expenses  connected  with  such 
shop  tests,  and  solicit  subscriptions  on  this  account  from  railroad 
companies  and  locomotive-builders." 

A  few  weeks  later,  at  the  summer  meeting  of  the  American  Society 
of  Mechanical  Engineers,  a  paper  giving  results  of  twenty  efficiency 
tests  upon  the  Purdue  locomotive  was  presented,*  and  at  this  meet- 
ing, also,  the  committee  appointed  to  report  upon  standard  methods 
of  conducting  locomotive  tests  presented  a  document  f  dealing  in 
a  comprehensive  manner  with  the  question  at  issue,  giving  liberal  atten- 
tion to  shop  tests  and  recommending  such  tests  as  the  only  satisfactory 
method  of  settling  the  important  questions  of  performance.  As  a  re- 
sult of  this  report  a  resolution  was  proposed  calling  for  a  committee  to 
cooperate  with  the  committee  of  the  American  Railway  Master 
Mechanics'  Association  in  carrying  out  investigations  at  Purdue. 
At  the  next  regular  meeting  of  the  Society,  however,  the  council  to 
whom  the  above-mentioned  resolution  was  referred  reported  that 
such  a  resolution  was  deemed  inexpedient,  and  further  consideration 
of  the  matter  by  the  Mechanical  Engineers  was,  therefore,  dropped. 

Meanwhile  it  was  being  urged  by  the  Master  Mechanics'  Associa- 
tion that  funds  and  locomotives  should  be  made  available  for  work 
upon  the  Purdue  plant,  and  while  the  movement  here  was  also  des- 
tined to  failure,  so  far  as  the  immediate  purpose  in  view  was  con- 
cerned, the  discussion  and  reports  during  the  years  1893  to!895  leave 
no  doubt  as  to  the  attitude  of  the  Association  with  reference  to  the 
value  of  laboratory  tests  of  locomotives. 

21.  New  Plants. t — In  view  of  the  value  of  the  locomotive-testing 
plant  as  a  means  of  determining  the  performance  of  locomotives,  it 
was  reasonable  to  expect  that  the  number  of  such  plants  would 
increase.  The  first  to  be  completed,  following  lines  developed  at 
Purdue,  was  that  of  the  Chicago  &  Northwestern  Railroad  Com- 
pany, which  went  into  commission  in  the  year  1895;  the  next  that 
of  Columbia  University,  built  in  1899.  Following  these  came  various 
plants  for  railroad  companies  and  technical  institutions  both  in  this 
country  and  abroad,  among  which  the  most  deserving  of  mention 
at  this  time  (1906)  is  probably  that  of  the  Pennsylvania  Railroad 
Company  installed  at  St.  Louis  during  the  Exposition  of  1904  and 
afterwards  removed  to  the  Company's  shops  at  Altoona. 

*  "  Tests  of  the  Locomotive  at  the  Laboratory  of  Purdue  University."  Trans- 
actions of  the  American  Society  of  Mechanical  Engineers,  Vol.  XIV,  pp.  826-854. 

f  Transactions  of  the  American  Society  of  Mechanical  Engineers,  1893,  pp. 
1312-1339. 

J  Transactions  cf  the  American  Society  of  Mechanical  Engineers,  Vol.  XXV, 


CHAPTER  III. 

i 

LOCOMOTIVE  SCHENECTADY  NO.  1. 

22.  The  Controlling  Conditions  Affecting  the  Choice  of  a  Loco- 
motive which  should  serve  the  purposes  of  the  laboratory  were 
the  outcome  of  a  desire  to  have  the  machine,  in  size  and  in  the  char- 
acter of  its  details,  fairly  representative  of  good  American  practice 
at  the  time  the  order  was  given;  that  is,  in  1891.  The  type  of  loco- 
motive and  the  size  of  its  cylinders  were  the  only  points  prescribed 
by  the  University  authorities.  The  details  of  the  design  were  left  to 


FIG.  29. — Elevation  of  Schenectady  No.  1. 

the  discretion  of  the  builders,  who,  being  thus  untrammeled,  pro- 
duced an  engine  which  it  is  presumed  represented  their  standard 
practice.  There  were  heavier  and  more  powerful  engines  in  use, 
but  there  were  also  very  many  which  were  lighter  and  of  less  power. 
The  locomotive  was  in  every  respect  normal.  No  fixture  or  fitting 
was  omitted  which  was  then  in  common  use  on  the  road.  It  had 
air-brakes  and  a  headlight,  and  had  it  been  coupled  to  a  tender 
and  placed  at  the  head  of  a  train,  it  would  have  lacked  nothing  for 
the  service  which  might  then  have  been  demanded  of  it.  Neither 

46 


LOCOMOTIVE  SCHENECTADY  No.  1.  47 

was  there  any  detail  of  consequence  added  or  modified  by  the  builders 
to  especially  adapt  the  machine  to  the  purposes  of  the  laboratory. 

The  locomotive,  therefore,  being  representative  in  size  and  nor- 
mal in  character,  it  was  but  reasonable  to  expect  that  results  obtained 
from  it  would,  in  their  general  aspect  at  least,  apply  to  a  very  large 
class  of  American  locomotives. 

23.  Specifications  as  prepared  by  the  builders  are  as  follows: 

SCHENECTADY  LOCOMOTIVE  WORKS. 

SCHENECTADY,  N.  Y,  April,  1891. 
SPECIFICATION  No.  1491. 

Eight-wheel  Locomotive  Engine  for  Purdue  University:  Engine 
Schenectady,  No.  1. 

GENERAL   DESCRIPTION. 

Gauge  4  feet  8£  inches.     Fuel,  bituminous  coal. 
Cylinders  17"  diam.,  24"  stroke.     Drivers  63"  diam. 
Driving-wheel  base  8  ft.  6  in.     Total  wheel-base  22  ft.  11  in. 
Weight  in  working  order,  on  drivers,  about  56,000  Ibs. 
Total,  about  85,000  Ibs. 

CONSTRUCTION. 

BOILER.  To  be  of  the  best  workmanship  and  material,  to  be  capable  of 

carrying  with  safety  a  working  pressure  of  140  Ibs.  per  square 
inch,  and  of  sufficient  capacity  to  supply  steam  economically. 
All  horizontal  seams  quadruple-riveted  with  welt-strip  inside. 
A  double-riveted  seam  uniting  waist  with  fire-box.  All  plates 
planed  at  edges  and  calked  with  round-pointed  tools.  Boiler 
to  have  extended  front  end.  Waist,  dome,  and  outside  of 
fire-box  of  steel  •%%'  thick.  Diam.  of  waist  at  front  end  52", 
made  wagon-top,  with  one  dome  30"  diam.  placed  on  wagon- top. 

FIRE-BOX.  Of  best  quality  fire-box  steel,  72"  long,  34f"  wide,  73"  deep. 

Crown-sheet  three-eighths,  tube-sheet  one-half,  side  and  back 
sheets  five-sixteenths  thick.  Water-space  4"  front,  3"  sides, 
3"  back.  All  sheets  thoroughly  annealed  after  flanging. 

Stay-bolts  \  and  1  inch  diam.,  screwed  and  riveted  to  sheets, 
and  placed  not  over  4  inches  from  center  to  center. 

Crown-sheet  supported  by  crown-bars  made  of  two  pieces 
of  wrought  iron  5"  wide,  f "  thick,  placed  not  over  4£  inches 
apart,  reaching  across  crown  and  resting  on  edge  of  side-sheets. 
Crown-bars  riveted  to  crown-sheets,  with  seven -eighth -inch 
rivets  placed  not  over  4|  inches  from  center  to  center,  each 
bar  having  four  stay-braces  to  top  of  boiler  or  dome. 


48 


LOCOMOTIVE  PERFORMANCE. 


TUBES.  Of  charcoal-iron,  200  in  number,  2"  diam.,  11  ft.  6  in.  in  length. 

Set  with  copper  ferules  at  both  ends. 

Cleaning-holes  at  the  corners  of  fire-box,  and  blow-off  cock 
on  back. 

GRATE.  Grates,  rocking.     Ash-pan  with  dampers  front  and  back. 

STACK.  Smoke-stack  straight.     Deflecting-plate  and  netting  in  smoke- 

box. 

FRAMES.  Of  best  hammered  iron,  main  frame  in  one  section  with  braces 

welded  in.  Forward  section  securely  bolted  and  keyed  to  main 
frame.  Pedestals  protected  from  wear  by  cast-iron  shoes  and 
wedges,  and  locked  together  at  bottom  by  bolt  through  cast- 
iron  thimble.  Width  of  main  frame  4". 

CYLINDERS.  Of    close-grained    hard    charcoal-iron.      Cast    with    half-saddle 

attached,  the  right  and  left  cylinders  from  the  same  pattern 
and  interchangeable.  Fitted  together  in  a  substantial  manner 
and  securely  bolted  and  keyed  to  frame.  Valve-face  and  steam- 
chest  seat  raised  above  face  of  cylinder  to  allow  for  wear. 
Cylinders  oiled  from  N.  &  Co.  No.  8  sight-feed  lubricator  placed 
in  cab,  with  copper  pipe  under  boiler-lagging  to  steam-chest. 

THROTTLE.  Balanced  valve  placed  in  dome,   with   wrought- iron   dry- pipe 

and  cast-iron  steam-pipe  connecting  to  cylinders. 

PISTONS.  Made  with  removable  followers,  or  with  solid  heads,  and  fitted 

with  approved  steam-packing. 
Piston-rods  of  hammered  iron. 

VALVE-MOTION.  Approved  shifting  link-motion  graduated  to  cut  off  equally  at 
all  points  of  the  stroke.  Links,  sliding-blocks,  plates,  lifting- 
links,  pins,  and  eccentric-rod  jaws  of  the  best  hammered  iron, 
thoroughly  case-hardened.  Steam-chest  valves,  Richardson 
balanced. 

GUIDES.  Of  hammered  iron,  case-hardened. 

CROSS-HEADS.  Of  cast  steel  with  brass  gibs.     Style  for  four  bar-guides. 

DRIVING-WHEELS.  Four  in  number,  63"  diam.  Centers  cast  of  the  best  charcoal- 
iron  and  turned  to  57"  diam.  to  receive  tire. 

TIRES.  Of  American  steel,  3"  thick,  both  pairs  flanged  5f"  wide. 

AXLES.  Of  hammered  iron,  with  journals  7"  diam.  8"  long.  Driving- 

boxes  of  cast  iron,  with  heavy  Damascus  bronze  bearings  and 
large  oil- cellars. 

SPRINGS.  Made  of  the  best  cast  steel,  tempered  in  oil.  Secured  to  a 

system  of  equalizing- beams  to  insure  the  engine  riding  in  the 
best  possible  manner. 

RODS.  Connecting  and  parallel  rods  of  hammered  iron  or  steel,  each 

forged  solid,  fitted  with  all  necessary  straps,  keys,  bolts,  and 
brass  bearings. 


LOCOMOTIVE  SCHENECTADY  No.  1. 


49 


CRANK-PINS.  Of  steel. 

WATER-SUPPLY.  To  have  two  injectors  (Monitor  No.  8  R.  H.,  No.  7  L.  H. )  with 
well- arranged  cocks  and  valves  for  convenience  in  working. 

ENGINE-TRUCK.  With  square  wrought-iron  frame,  cast-iron  pedestals,  and  center 
bearing  suitable  for  rigid  center,  with  approved  arrangement 
of  equalizing  beams  and  springs. 

WHEELS.  Four    double-plate    chilled    wheels    of    first-class    manufacture, 

28"  diameter. 

AXLES.  Of  hammered  iron,  with  inside  journals  5"  diam. ,  9"  long.    Springs 

of  best  cast  steel,  tempered  in  oil. 

CAB.  Constructed  of  seasoned  ash,  substantially  built,  and  secured 

by  joint- bolts  and  corner- plates.  Furnished  with  seats  and 
tool- boxes  for  engineer  and  fireman. 

PILOT.  Of  wood,  strongly  braced,  and  provided  with  substantial  draw- 

bar. 

FINISH.  Boiler   lagged  with    wood    and    jacketed  with    planished    iron, 

secured  by  planished  iron  bands.  Dome  lagged  with  wood, 
with  sheet-iron  casing  and  cast-iron  rings  painted.  Cylinders 
lagged  with  wood,  with  sheet- iron  casing  and  cast-iron  head- 
covers  finished.  Steam-chests  cased  with  sheet  iron,  with  cast, 
iron  covers  finished.  Hand-rail  of  iron  finished,  with  columns 
secured  to  boiler. 

Boiler  front  and  door  of  cast  iron. 

FIXTURES  AND  Engine  provided  with  sand-box,  support  for  headlight,  bell, 
FURNITURE.  whistle,  steam-gauge,  gauge-cocks,  cab-lamp,  blower,  oil-cans, 

torch;  also  all  necessary  wrenches,  fire-tools,  hammers,  chisels, 
packing- tools,  etc. 

Two  jack-screws  and  a  pinch- bar. 

Principal  parts  of  engine  fitted  to  gauges  and  templates, 
and  interchangeable. 

All  finished  removable  nuts  case-hardened.  I.  A.  Williams 
&  Co.  headlight. 

All  threads  United  States  standard. 

PAINTING.  Engine  to  be  well  painted  and  varnished,  with  the  road,  number 

mark,  and  name  put  on  in  handsome  style. 

PATENTS.  All  patent  fees  not  covered  by  this  specification  excepted. 

BRAKE.  Westinghouse  automatic  air-brake  on  drivers. 


24.  Drawings   of    the    locomotive  as  covered  by  the  preceding 
specifications  follow  the  text  of  this  chapter. 

25.  Constants. — In  calculating  the  performance  of  the  locomotive 
from  observed  data,  use  is  made  of  various  dimensions,  relationships, 


50  LOCOMOTIVE  PERFORMANCE. 

and  calculated  values,  which  for  convenience  are  herein  grouped 
under  a  single  head  as  " constants."  The  dimensions  upon  which 
some  of  these  values  are  based,  as,  for  example,  cylinder  diameters, 
are  subject  to  slight  change  resulting  from  use  or  repairs;  and  as  the 
tests  in  question  extended  .over  a  period  of  several  years,  and  as 
they  were  interrupted  by  the  necessity  of  giving  the  locomotive 
general  repairs,  the  values  used  as  constants  were  carefully  watched 
and  frequently  checked.  All  changes  observed  were,  however,  too 
small  to  merit  consideration  excepting  those  which  occurred  in  the 
diameter  of  the  cylinder  at  the  time  the  engine  was  put  through 
general  repairs  in  1894.  After  this  date  certain  values  which  had 
previously  prevailed  could  no  longer  be  employed,  and  it  will  be 
noted  that  the  tabulated  statement  exhibits  two  sets  of  constants 
for  such  factors. 

At  the  time  these  tests  were  made,  authorities  disagreed  as  to 
the  method  of  measuring  the  extent  of  heating  surface  in  boilers, 
some  advocating  the  use  of  the  inner  surface,  while  others  favored 
the  use  of  the  outer  surface  of  the  tubes.  The  general  practice  in 
locomotive  work  had  been  to  employ  the  outside  of  the  tube.  In 
the  Purdue  work,  for  reasons  which  appeared  logical  the  heating  sur- 
face was  defined  as  the  inside  surface  of  the  fire-box  plus  the  inside 
surface  of  the  tubes  plus  the  effective  surface  of  the  front  head. 

A  summary  of  the  principal  dimensions  of  the  experimental 
locomotive  and  of  constants  used  in  calculating  results  derived  from 
tests  is  as  follows: 

Total  weight  (makers'  figures) 85,000  pounds. 

Weight  on  four  drivers  (makers'  figures) 56,000        " 

Total  wheel-base 22  ft.  11  in. 

Driving-wheel  base 6  "    6    " 

Nominal  cylinder  diameter 17  in. 

Nominal  stroke  of  piston 24    " 

Diameter  of  piston-rods 3    " 

Area  of  piston-rod  section 7.07  sq.  in. 

Prior  to  Subsequent  to 

Jan.  24,  1894.  Jan.  24,  1894. 

Actual  cylinder  diameter  (inches): 

Right  side 17  17.047 

Left  side 17  17.031 

Actual  stroke  of  pistons  (inches): 

Right  side 24  23.936 

Leftside..  24  23.889 


LOCOMOTIVE  SCHENECTADY  No.  1. 


51 


Prior  to 
Jan.  24,  1894. 

Effective  area  of  pistons  (square  inches): 

/Headend 226.98 

RlghtSlde\Crankend 219.91 

/Headend 226.98 

Leftside  \Crankend 219.91 

Piston  displacement,  cubic  feet: 

/Headend 3.1525 

Right  side  \  ~      .        ,  0  AK/m 

I  Crank  end o .  Uo4U 

/Headend.  ...  3.1525 

LeftSlde     \Crankend 3.0540 

Clearance  volume,  per  cent  of  piston  displacement: 

/  Head  end 9.390 

Right  side  \  1A  Oft_ 

I  Crank  end 10 . 265 

/Head  end.  ...  9.980 

Left  side     s  _,      ,         ,  .,.  _._ 

I  Crank  end 10.019 

INDICATED  H.P.  CONSTANT,  or  the  horse-power  for 
one  pound  mean  effective  pressure  and  a  speed 
of  one  revolution  per  minute. 

/Headend 01375 

Right  side  (Crankend 01332 

f  Head  end 01375 

I  Crank  end.  ..  .01332 


Subsequent  to 
Jan.  24,  1894. 


228.23 
221.16 

227.82 
220.75 


3.1617 
3.0637 
3.1497 
3.1520 


9.103 
10.046 
10.086 

9.880 


.013796 
.013368 
.013744 
.013318 


ractive  H.P.  Constant,  or  the  horse-power  devel- 
oped at  the  draw-bar  when  there  is  a  pull  of  one 
po.ind  and  a  speed  of  one  revolution  per  minute.  . 


.0004981 


.0004956 


Drivers: 

Nominal  diameter,  inches 63 

Actual  circumference,  inches 197.25 

Actual  diameter,  inches 62. 7 


63 

196.25 
62.47 


Ports: 

Length,  inches 16 

Width  of  steam-ports,  inches 1  £ 

Width  of  exhaust-port,  inches 2  J 


Valves: 

Type— "D"  slide. 

Design — Richardson  balanced. 


52 


LOCOMOTIVE  PERFORMANCE. 


The  proportions  and  the  setting  of  the  valves  were  changed  for 
different  series  of  tests  as  follows: 


Reference  Symbols. 


No.  appearing 
in  Col.  5, 
Table  I. 

I 

II 
III 

IV 

V 

VI 

VII 

VIII 

IX 

£ 

XI 


Series. 


Outside  Lap. 
Inches. 


Inside  Lap. 
Inches. 


Inside 

Clearance. 

Inches. 


A 


Valve-setting. 


Builders' 
Lead  Reduced 


Eccentrics 
Advanced 


Boiler: 

Diameter  waist  at  front  end,  inches 52 

Diameter  tubes,  outside,  inches 2 

Diameter  tubes,  inside,  inches 1 . 78 

Number  of  tubes 200 

Length  of  tubes,  feet. 11.5 

Thickness  of  tubes,  inches .11 

Area  of  flameway  through  tubes,  feet 3.46 

Width  of  fire-box,  inches 34.5 

Length  of  fire-box,  inches 72 

Height  of  fire-box,  inches 73 

Heating  surface,  square  feet: 

In  fire-box 132. 1 

In  front  head 10.5 

In  tubes  calculated  from  outside  diameter 1204.3 

In  tubes  calculated  from  inside  diameter 1071 .8 

Total  heating  surface  assuming  the  tube  surface  to  be  calculated  from 

the  outside  diameter 1346.9 

Total  heating  surface  assuming  the  tube  surface  to  be  calculated  from 

the  inside  diameter.* 1214.4 

Grate  area,  square  feet 17.25 

Ratio  of  heating  surface  to  grate  area:. 

Assuming  heating  surface  to  be  1214.4  sq.  ft 7.04 

Pounds  of  water  in  boiler  when  filled  to  middle  gauge 8450 

Steam-space  in  boiler  when  filled  to  middle  gauge,  cubic  feet 52 . 8 

Ratio  of  steam-space  to  entire  cubical  capacity  of  boiler .29 

Exhaust  nozzle,  double. 


*  This  factor  has  been  used  in  all  calculations  involving  heating  surface. 


LOCOMOTIVE  SCHENECTADY  No.  1. 


53 


Weight  of  parts  connecting  with  crank-pins: 

Piston  and  piston-rod,  pounds 297 .0 

Cross-head  with  part  of  indicator  rigging  attached,  pounds 170.5 

Main  rod,  pounds 344. 5 

Side  rod,  pounds 278 .0 

26.  Steam-passages. — The  areas  of  the  several  steam-passages 
between  the  throttle  and  the  exhaust-tips  through  which  the  steam 
passes  are  shown  graphically  with  great  clearness  in  the  diagram 
Fig.  54.  By  use  of  this  diagram  in  connection  with  the  recorded 
data  of  tests  it  should  be  possible  to  make  an  approximate  deter- 
mination of  the  steam  velocity  at  various  points  in  its  course. 


HALF  PLAN  OF  PIPE       HALF  PLAN  OF  NOZZLE 


FIG.  30.— Stack. 


FIG.  31. — Exhaust-pipe  and  -nozzle. 


54 


LOCOMOTIVE  PERFORMANCE. 


FIG.  32. — Dry-pipe. 


FIG.  33. — Branch-pipe. 


LOCOMOTIVE  SCHENECTADY  No   1. 


55 


p 

E. 


I 


56 


LOCOMOTIVE  PERFORMANCE. 


LOCOMOTIVE  SCHENECTADY  No.  1. 


57 


58 


LOCOMOTIVE  PERFORMANCE. 


FIG.  37. — Valve-box  and  Cover. 


LOCOMOTIVE  SCHENECTADY  No.  1. 


59 


60 


LOCOMOTIVE  PERFORMANCE. 


FIG.  39. — Piston  and  Piston-rod. 


I  ° 

0       o       ° 

0                      0 

jit        \«  . 

—  »*-  i  w^-* 

co            co 

a  1     L!r 

—  ^ 

_ 

.___. 
0          °          0 

~" 

O" 

•<c* 

FIG.  40. — Cross-head. 


LOCOMOTIVE  tiCHENECTADY  No.  1. 


61 


m 


FIG.  41. — Guides  and  Guide-yoke. 


62 


LOCOMOTIVE  PERFORMANCE. 


[     Half  rian  of  Bottom 


%  Plan  of 
Top  without  Strips 


k 7-K- , J 

iu — 5-K- *n 


I      \< 


FIG.  42.— Valve. 


-2B^- 


FIG.  43. — Valve-yoke. 


O-'' 


FIG.  44. — Steam-chest  Valve-rod. 


LOCOMOTIVE  SCHENECTADY  No.  1. 


FIG.  46. — Link  and  Link-block. 


64 


LOCOMOTIVE  PERFORMANCE. 


IT* 


*s 

AY*> 

5 

\ 

f 

< 

\ 

!    1   ^r 

t 

(I 

a 

FIG.  47. — Eccentric  Rod. 


Drip  Ploy 


FIG.  48. — Eccentric  Strap. 


LOCOMOTIVE  SCHENECTADY  No.  L 


65 


FIG.  49. — Eccentric. 


FIG.  50. — Reverse-shaft. 


66 


LOCOMOTIVE  PERFORMANCE. 


c 


FIG.  51. — Reverse-lever  and  Quadrant. 


FIG.  52. — Throttle-lever. 


LOCOMOTIVE  SCHENECTADY  No.  1. 


67 


FIG.  53.— Throttle  and  Throttle.pipe. 


68 


LOCOMOTIVE  PERFORMANCE 


< 


Throttle  Port 
Throttle  Pipe 


90    ~rOD"       : 
~G.  i  do 


Elbow  between  Throttle  and  Dry  Pipe 
Dry  Pipe 

Body  of  T- Fitting  in  Smoke  Box 


33.6C" 


32.131?; 


3i.81D" 


^Branches  of  T-Fitting  in  Smoke  Box 
Branch  Pipes  in  Smoke  Box 
Openings  into  Saddle  ( 

Steam  Ports  in  Valve  Seat 


G0n       Exhaust  Pass;io-es  in 


Exhaust  Tips 

FIG.  54. — Steam-passage  Areas. 


CHAPTER  IV. 

METHOD   OF   TESTING    AND   DATA. 

27.  Method  of  Testing. — In  preparation  for  a  test  the  locomo- 
tive was  run  for  an  hour  or  two  in  the  morning  at  low  speed  and 
light  load.  After  the  noon  stop  it  was  again  started  with  the  reverse 
lever  in  the  position  which  it  was  to  occupy  during  the  test,  while 
the  load  was  gradually  thrown  on  and  the  speed  increased  until  the 
predetermined  conditions  for  the  test  had  been  attained.  At  the 
stroke  of  a  gong,  usually  between  ten  and  thirty  minutes  after  start- 
ing, all  readings  were  taken  and  the  test  was  commenced.  The 
throttle  was  seldom  touched  after  starting  a  test.  Variations  in 
boiler  pressure  during  a  test  were  so  slight  that  changes  in  speed 
caused  thereby  were  easily  controlled  by  increasing  or  decreasing 
the  brake  load.  At  the  end  of  the  test  care  was  taken  to  have  the 
water  in  the  boiler  at  the  same  level  and  the  fire  in  the  same  con- 
ditions as  at  the  start.  Then  upon  the  stroke  of  the  gong  the  throttle 
was  closed  and  the  fire  immediately  dumped  and  quenched.  Four 
regular  attendants  of  the  laboratory,  including  a  fireman,  prepared 
the  locomotive  for  test,  and  during  the  tests  fired  the  boiler  and 
gave  all  necessary  attention  to  the  mounting  and  accessory  machinery, 
A  corps  of  student  observers  working  under  the  direction  of  an  in- 
structor acting  as  supervisor  of  tests  was  responsible  for  all  the 
observations.  Students  thus  employed  were  generally  seniors  in  the 
Department  of  Mechanical  Engineering.  Twelve  observers  were  re- 
quired, stationed  as  follows: 

Number  of 
Observers. 

To  keep  running  log,  time,  and  gong ' 1 

To  weigh  fuel;   also  to  note  time  of  starting  and  stopping  injector,  and 

to  keep  log  of  same 2 

To  weigh  feed- water,  to  observe  temperature,  and  to  keep  log  of  same       2 
To  operate  indicators;    also  to  take  calorimeter  readings,  dry-pipe 

pressure,  draft-gauge,  and  pyrometer  readings ".       4 

To  read  engine  and  supporting- wheel  counters   and  dynamometer; 
also    to  read    boiler  pressure,  and  regulate  the  water  pressure 

upon  the  several  brakes 2 

To  occupy  the  engineer's  box 1 

12 
69 


70 


LOCOMOTIVE  PERFORMANCE. 


ENGINEERING  LABORATORY. 


Of  Tat  Jfa 2£l/__S«ri«,_£ 


RUNNING  LOG 


PURDUE  UNIVERSITY. 


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FROM    PARTIAL   LOGS. 

»  of  feed-wator  delivered  to  Injector. £/6¥7+6  Xlll.«-  Quality  o«  .team  In  D«me 


...  C«<iZ.  ______ 


<> 

..................  .  ______  Jg.7z.ze~ 

,  __________   ZSLffL 


xxTi. 

XXIII. 


MOTES; No   water  JL^^^  ,_. 


FIG.  55. 


METHOD   OF   TESTING  AND  DATA. 


71 


As  the  readings  were  taken  they  were  entered  on  the  appropriate 
logs,  facsimiles  of  which  are  shown  in  Figs.  55-60.  The  card  log  and 
the  summary  sheet  (Figs.  59  and  60)  were  filled  out  later  as  the  test 
was  worked  up,  the  card  log  containing  all  the  indicator-card  measure- 
ments, while  the  summary  sheet,  as  its  name  implies,  comprises  all 


FEED-WATER    LOG. 

Test  No...  45-J..  ..Series./?  ......  .....      Locomotive..  .". 

Observer.  ____Ha8LJin.  ______________          Date.  .  .Nov..  ££,. 


1695 


LEFT    BARREL. 

RI&HT    B/JRREL. 

Check. 

" 

Time. 

Check. 

Time,. 

Check. 

Time 

Temjo. 

Chech. 

Time,. 

Temp. 

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Right  Barrel  -  -  -  Times  Emptied. .  2.7#  .  Calibrated  WL.32J.  _M.  of  WaUr.lQ?9£ti 
Rveraje  Temperature..  .364 ¥:  Total  Wt.  ofWater.£l6f_?& 

/Vote.  ..OflLld.  OF  LOST  J3/IRR£L  .  UfiEO, , _ i 

FIG.  56. 

the  final  calculated  and  observed  results  from  the  test,  together  with 
the  constants  and  dimensions  of  the  engine. 

28.  Data. — The  tables  at  the  end  of  this  chapter  present  the 
results  of  forty-four  efficiency  tests  made  upon  locomotive  Schenec- 
tady  No.  1.  These  tests  are  not  all  that  were  run  during  the  period 


72 


LOCOMOTIVE  PERFORMANCE. 


covered,  but  they  comprise  all  the  later  tests  and  have  been  chosen 
as  those  concerning  the  reliability  of  which  no  doubt  can  be  enter- 
tained. Only  final  results  are  given,  which,  in  the  case  of  observed 
data,  are  generally  the  average  of  observations  made  at  five-minute 
intervals  and  checked  either  by  two  different  observers  or  by  one 
observer  and  some  form  of  automatic  recording-instrument.  In 


ENGINEERING  LABORATORY. 


FUBL  LOG 


1 

2 

3 

4 

5 

1 

2 

3 

4 

5 

Tim  of 
Cong. 

tVeisMof 

run  BO*. 

Weight  'of 

Empty  Bo,. 

Weight  of 

Tim*  of 
Gang. 

Mi?«  of 
FuZI  Bar. 

Weight  of 
Em^ty  flo». 

WeioAt  of 

Coal. 

•  I  :is 

2.55 

332, 

0 

238. 

323. 

93. 

2=50 

^IS 

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93 

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3.55 

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25O. 

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2.45 

4.'05 

2-50 

MO 

*.\5 

WafM  of dry  coal  find. 


Weifht  of  coat  fired  _ 


d.    trrctnt.  of  uata-M  coal  find. 


dry  andert  caufU  in  tmoke  tax* 


FIG.  57. 

the  case  of  derived  results  the  calculations  have  been  made  by  two 
or  more  independent  workers  and  carefully  checked. 

That  the  facts  may  be  more  readily  apprehended  the  results  are 
divided  into  nineteen  tables  grouped  under  four  heads,  namely, 
General  Conditions  (I -III),  Boiler  Performance  (IV-VII),  Engine 
Performance  (VIII-XVI),  Locomotive  Performance  (XVII-XIX). 


METHOD  OF  TESTING  AND  DATA. 


73 


Each  test  is  designated  by  Consecutive  Number,  by  Laboratory 
Symbol,  and  by  Date.  The  Laboratory  Symbol  tells  at  a  glance 
the  speed  in  miles  per  hour,  the  position  of  the  reverse-lever,  and 
the  series  to  which  the  test  belongs.  Thus  15-1-A  denotes  a  test 
run  at  a  speed  of  fifteen  miles  per  hour,  with  the  reverse-lever  in 
the  first  notch  forward  of  the  center  and  under  the  conditions  of 
Series  A.  The  conditions  of  valve-setting  and  proportions  which 


ENGINEERING  LABORATORY  PURDUE  UNIVERSITY. 

Test  for  Determining  the  Quality  of  Steam 

BY   USE  OF  THROTTLING  CALORIMETER  No 

Tests  made  in  connection  with LOCOMOTIVE     TgST = JVb.   ^5~/-fl 

Mad*  by  K/MWUBQJ —  Ztofe   /VoVEMBEff    £Q 189*.. 


Goi.fr 

Numter 

Tim* 

Differ- 

Steam 
by  Gauge 

«U,m< 

Frimn  11 
hltnnui 
>!««•!• 

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NOTES 

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Barometric  Pressure 

Jlsolute  Steam  Pressure 

Temperature  corresponding  with  Steam  Pressure- 
Absolute  Pretsure  in  Calorimeter 

Temperature  corresiioiuling  with 


351.  72 


(a>  QUALITY  OF  STEAM  I 

Per  cent  of  Priming 


/.S? 


19. 


226.07 


FIG.  58. 

distinguished  the  various  series  are  listed  under  Constants.  Through- 
out this  set  of  tables  the  tests  are  arranged  in  series,  with  low  speeds 
and  early  points  of  cut-off  first  in  each  series,  and  for  con- 
venience in  comparison  and  reference,  the  Consecutive  Numbers 
and  Laboratory  Symbols  are  reprinted  with  each  table.  In  succeed- 
ing chapters  it  has  been  found  convenient  in  some  instances  to 


74 


LOCOMOTIVE  PERFORMANCE. 


select  certain  data  and  present  them  rearranged  to  suit  the  matter 
in  hand.  In  all  such  cases  the  Laboratory  Symbol  affords  a  ready 
means  of  identification. 

The  following  concerns  the  several  items  appearing  in  the  tables 
and  the  methods  of  computation: 


aronraanrauBORATOBT.  PURDUE  UNIVERSITY. 

PRESSURES  AS  OBTAINED  FROM  INDICATOR  CARDS. 

fell  Jfa^ir/jS~ I  .  fieri  ** Q_ Of  7./*vmt,/rfiW         $ C. ^4 gftf  £^ T/f  Q Y-    _,L-  $faf7jt-NQV£M$ER_£0     ___t89_£_ 


Sprint  of  Card*         60  R>  (*M  OS  . 


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30. 3T3 


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jfhvlute  Preuurt  at  Cut-off, 


TLZOf 


Absolute  Mean  Back-Fn 


16.46% 


FIG.  59. 

Item  1. — Consecutive  Number. 

Item  2. — Laboratory  Symbol. 

Item  3. — Date  of  Running  Test. 

Item  4. — Duration  of  Test  in  Minutes. 


METHOD  OF   TESTING  AND  DATA. 


75 


CNeiNEumOLAiORATOiir.  SUMMARY   OF   RESULTS.  m 

'......mm.: _ Afav,..£Q+.., ..i»«J'..o,  LOCOMOTIVE.... .."5cHt-Ar£C7/».o.y 

TffAQQT     fiNO   ..CJK.Wot.ee Checked  by R^.M'UjZfi  .., 

CONCERNING    THE    LOCOMOTIVE. 

Tolal  weight,  Ibs TSfOOQ...., Cireumlereneo  of  driven,  It 16.3.53....         Total  are.  M  healing  sarhee. &9..fttt. 

Worghto.  ./?...  .eViven ....56,000. Ota.  ol  boiler,  inches ...*$£.« Area  d  grate  surface  .  -J.9- .  Fut. . . . . . 

•rtfe  el  piston 23,.^/^.....         Length  d  tube,  Art ..//,»f. 

Dt'i  ot  drivers 


CONSTANTS    FOR    TEST. 


|  l«.r  in  ./J.t.....wlck  Irom  oenlw 


Tractive  lorte  assumed  to  be  necessary  to  draw  one  ten 
on  level  track  at  speed  o(  tesl .  ., 


.«..,.. 

Clearance,  per  cent,  ol  piston  displacement  . 


3,!6l£>tti>. 

..   A?f 


...,9/XMfT    ...OJ.37WI. 
&M...  ...    ./,.?*  ..:. 


Beginning  ol  compression,  per  cent  ol  itroko. 


.LOJ3.6&79  JJffllSVI. 


...  1,000 Jtf.6 


:.**7!ffKf 

RESULTS    FROM    THE    INDICATOR. 

Initial  pressure „ ///.#..       ......l/Lt. I.I?,Q.         ....U.7..?. //«,<T. 

Pmsure  >t  cut** .... , , • 63*7...      .......%..7 67,6      \ 7/:6 67,.?.. 

•acupressure... A.. t ; ^.2 |?,.ff.       .'.,&7.       &-T. «'.f*.' 

Prewife  at  the  beginnlnj  ol  compression t '.. .- '.-.i.. £.?.:(! .?.?.'. f&*3.        ....»?.•?;/.. 

•«n  efl«.we  press^ : -..., ...Jfat..       ...,.£&ft..      ZZ3 .^f.f.. 

RESULTS    FROM.    LOOS    OF    TEST. 

lie     Temperature  el  smoke  bm......'........6$$'3S...  Hi  Kind  ol  fuel 

Ki«    Temperature  ol  laboralorj ?$•(>. .....  $«  Pound,  ol  dry  coal 

Lv     Temperature  ol  teed  water  .' $6:3....  Tr  Pounds  ol  dry  ash  . 

Ell    Seller  pressure -.-. .....: t£f*T&...        IJTOJ  Pounds  o(  waler  delivered  to  belkjr  m*  U, 

Cio    •aromelric  pressure ..../&30T..        Ntn    Pounds  water  lost  Iron  boiler f/.:.7£ 

Mil    Height  el  water  I*  gauge-  0      Pounds  (lean  uppll 

tUM .• • -..-.. t    .  pu«l»y  ol  »let»  In  I 

CALCULATED    RESULTS. 

MtRtoHT"6t-ci     -  „.  ""'""•«..';.  -    "•«- 

t    Weight  ol  steam  at  euH(« ,,.„., ..,.•..., 

»   Weight  ol  steam  at  releite ....„ ,^.., 

4  Weight  el  steam  during  compression .-..., 

«    *e^apor»lionperH.P..eflK)iir....:.....4t^f66  .;.        .„    ejiin  ^  .,»..., ./ !. :...._...... f«,«?f<    M    Pe«»ds  ol  «eej  •*•  tadlctW  H.  P. 

.1    Weight  ol  sleam  per  rev.  by  W........:^?T?:?*.,/       18  'Or«mometer  H.  P. ,,...,...., ,.,....      •  iw  Me» .....'. 4<3tf.f.. 

5  Weight  ,1  mixture  In  cylinder,  19    Friction  ol  e-vjin,  I.  H.  P. ... > 29    Pounds  ol  teal  per  mile  run     ... 

""" * *M*K~.  20    FrhDM«^lM.»«rMri.rf  30  P^,  ^  c«.  M, .<«<•. 

9    Per  cent  ol  mixture  accounted  lor  M  ,  I.  H.>. .'.. ; 31  p,,,^,  ,,  ^,  ewewttef  eer 

steam  at  cut-ol! /7i..T/ 2l    OyMmonrtef  worli  In  l«ol  lon«,  ieime1  ol  e«tl '. 

10  Per  cent,  ol  mklure  accounted  (or  a,  per  pound  ol  stean  by  tank 32 

steam, I  release... ...,...f /•..<« „    o^m.mrtw  werl,  h,  tart  toM  «I2°F.. 

11  Pounds  ol  steam  per  indicated  H.  P.  _  per  pound  ol  dry  coal 3)    g,  T.  U.  take 

p..  K^t,,  Indicator. f.KfXftf.        23   CquW^  wei,bl  K  trrt,-*.  34    B.  T.  U.  tak«,  »p  p«  ^nd  M  ««,BHM»...  QSH/*. 

M    Pounds  ol  steam  per  indicated  H.  P.  -.  lens ,.ttt>.i. ,        35    e.  T.  U.  taken  up  by  boiler  per  H.  P. 

I*    •  ..-.. , .,  cars  ol  33  Ions  each -,„.„. r, ,.       35    Pounds  coal  per  loot  ol  grate  / 

**    ' • «!zni»«.— .•••• 28 ,.-.; 37    indkated  H.  P.  per  fool  ol  grate. 

»   ' - ~ 2. .        „    ... 


FIG.  60. 


76  LOCOMOTIVE  PERFORMANCE. 

Item  5. — Valve-setting  and  Proportions.  The  Roman  numerals 
here  refer  to  the  table  of  valve  proportions  under  Con- 
stants (Paragraph  25). 

Item  6. — Approximate  Cut-off  is  a  predetermined  condition  for  the 
test. 

Item    7. — Reverse- Lever,  notch  Forward  of  Center. 

Item    8. — Throttle  Position. 

Item  9. — Draw-bar  Pull  is  derived  from  the  known  value  of  the 
work  done  in  cylinders  and  of  that  lost  by  friction  = 
Item  134 -Item  136. 

Item  10. — Total  Revolutions  is  the  record  from  a  counter  attached 
to  the  rear  driver,  which  was  read  every  five  minutes 
as  a  check  on  the  regularity  of  running.  In  addition 
there  was  a  Boyer  railway  speed-indicator  reading 
in  miles  per  hour. 

Item  11. — Revolutions  per  Minute=Item  10-7-Item  4. 

Item  12. — Miles  Run  Equivalent  to  Total  Re  volutions = Item  10  X 
Circumference  of  Driver  in  feet  -f-  5280. 

Item  13.— Miles  per  Hour=Item  12 --(Item  4-T-60). 

Item  14. — Feed-water  Temperature  by  Thermometer. 

Item  15. — Laboratory  Temperature  by  Thermometer. 

Item  16. — Smoke-box  Temperature  is  the  record  obtained  from  a 
copper-ball  pyrometer  used  as  follows:  A  copper  ball 
of  known  weight  was  held  in  the  smoke-box  till  it  had 
presumably  attained  the  temperature  of  its  surround- 
ings, usually  about  forty  minutes,  and  was  then  allowed 
to  roll  quickly  down  a  tube  into  a  water  calorimeter. 
The  original  temperature  of  the  ball  was  computed 
from  data  thus  obtained. 

Item  17. — Boiler  Pressure  by  Gauge  is  the  record  of  readings  from 
an  ordinary  dial-gauge  at  intervals  of  five  minutes  as 
checked  by  a  recording-gauge. 

Item  18. — Atmospheric  Pressure  in  Pounds. 

Item  19. — Absolute  Boiler  Pressure =Item  17+Item  18. 

Item  20. — Dry-pipe  Pressure  by  Gauge. 

Item  21. — Times  Injectors  were  Started  includes  the  record  for  both 
right-hand  and  left-hand  injectors. 

Item  22. — Minutes  one  or  both  injectors  were  in  action.  Shows  the 
regularity  of  feed-water  supply. 

Item  23. — Draft  is  assumed  to  be  the  difference  in  pressure  between 


METHOD  OF  TESTING  AND  DATA.  7T 

the  atmosphere  and  the  interior  of  the  smoke-box,  as 
measured  by  a  U  tube  in  inches  of  water.  This  tube- 
was  fastened  securely  to  the  laboratory  wall,  having 
one  end  in  pipe  connection  with  the  interior  of  the 
smoke-box  and  the  other  open  to  the  atmosphere.  The 
pipe  entered  the  smoke-box  at  a  point  marked  C,  Fig.  35, 
Chapter  III.  Subsequent  experiment  has  shown  that 
this  is  not  the  point  of  least  pressure,  and  that  to  obtain 
the  actual  greatest  draft  these  values  should  be  mul- 
tiplied by  a  factor  of  1.3.  (See  Chapter  XI.) 

Item  24. — Water  Delivered  to  Boiler  and  Presumably  Evaporated 
is  the  actual  weight  of  water  delivered  to  the  injectors 
minus  the  weight  caught  from  the  injector  overflow. 
The  water  was  measured  by  means  of  two  carefully  cali- 
brated barrels,  one  of  which  was  filled  while  the  other 
was  being  emptied  into  the  receiving-tank.  A  water- 
meter  in  the  supply-line  served  as  a  check  to  prevent  any 
gross  error  in  measuring. 

Item  25. — Water  Lost  from  Boiler  is  the  weight  of  steam  used  by 
the  calorimeter  as  determined  by  previous  experiment. 
In  no  case  were  boiler  leaks  permitted. 

Item  26.— Steam  Supplied  Engine  =  Item  24 -I tern  25. 

Item  27. — Water  Evaporated  by  Boiler  per  Hour=Item  24  —  (Item 
4-60). 

Item  28. — Steam  Used  by  Engine  per  Hour=Item  26-=- (I tern  4-60).. 

Item  29. — Quality  of  Steam  as  indicated  by  the  throttling  calorimeter. 

Item  30. — Water  Evaporated  per  Square  Foot  Heating  Surf  ace = Item 
24-1214.4. 

Item  31. — Water  Evaporated  per  Square  Foot  Grate  Surface=Item 
24-17.25. 

Item  32. — Dry  Coal  Fired  is  the  total  weight  of  coal  less  the  amount 
of  accidental  moisture,  as  found  by  sample  taken  during 
each  test,  a  correction  which  seldom  exceeded  one  per 
cent. 

Item  33. — Dry  Ash  Caught  in  the  Ash-pan  during  the  Test.  Inas- 
much as  under  locomotive  conditions  a  large  per  cent 
of  the  non-combustible  material  goes  out  of  the  stack y 
the  weight  of  ash  was  not  used  to  determine  the  amount 
of  combustible  fired. 

Item  34. — Dry  Cinders  Caught  in  the  Smoke-box. 


78  LOCOMOTIVE  PERFORMANCE. 

Item  35.--Dry  Coal  fired  per  hour  =  Item  32 -f- (Item  4-60). 

Item  36. — Combustible  Fired  per  Hour  =  Item  35X0.9.  Through- 
out these  tests  the  fuel  used  was  Brazil  block  coal, 
mined  at  Brazil,  Indiana.  Frequent  analysis  of  the 
chemical  composition  showed  a  very  uniform  content 
of  combustible,  the  average  being  90  per  cent. 

Item  37. — Dry  Coal  per  Square  Foot  Heating  Surface  per  Hour  = 
Item  35-- 1214.4. 

Item  38. — Dry  Coal  per  Square  Foot  Grate  Surface  per  Hour  =  Item 
35 -f- 17.25. 

Item  39. — Same  as  Item  29. 

Item  40. — B.  T.  U.  taken  up  by  each  pound  of  Steam  is  the  result 
obtained  by  the  formula 

B.  T.  V.=q^-q0+xr, 

where  q  =  ihe  heat  in  one  pound  of  water  at  boiler  tem- 
perature, go  =  heat  in  one  pound  of  water  at  tempera- 
ture of  the  feed-water,  x  =  quality  of  steam  as  given  in 
column  39,  and  r  =  the  latent  heat  of  evaporation  at 
boiler  pressure.  (Peabody's  Steam-tables  used  for  all 
computations  involving  thermal  quantities.) 

Item  41. — B.  T.  U.  taken  up  by  Boiler  per  Minute  =Item  40Xltem 
27-60. 

Item  42.— B.  T.  U.  per  Pound  of  Coal  =  Item  40Xltem  27 -f- 1  tern  35. 

Item  43.— B.  T.  U.  per  Pound  of  Combustible  =  Item  40x1  tern  27 -f- 
Item  36. 

Item  44. — Water  Evaporated  per  Pound  of  Coal = Item  27 —Item  35. 

Item  45. — Water  Evaporated  per  Pound  of  Combustible = Item  27 -r- 
Item  36. 

Item  46. — Same  as  Item  27. 

Item  47. — Equivalent  Evaporation  per  Hour  =  Item  27  X Item  4  —  0 
latent  heat  of  evaporation  at  atmospheric  pressure 
(  =  965.8  B.  T.  U.). 

Item  48. — Equivalent  Evaporation  per  Square  Foot  Heating  Surface 
per  Hour=Item  47-1214.4. 

Item  49. — Equivalent  Evaporation  per  Square  Foot  Grate  Surface 
per  Hour  =  I  tern  47-17  25 

Item  50. — Equivalent  Evaporation  per  Pound  of  Dry  Coal = I  tern 
47-Item35. 


METHOD  OF  TESTING  AND   DATA.  7£ 

Item  51. — Equivalent  Evaporation  per  Pound  of  Combustible  = 
Item  47 + Item  36. 

Item  52. — Boiler  Horse-Power=Item  47-J-34.5. 

Items  53  to  102. — Events  of  Stroke  and  Pressures  above  Atmosphere 
from  Indicator-cards  need  no  explanation.  The 
same  point  on  the  card  was  used  to  determine 
the  event  of  stroke  and  the  corresponding  pres- 
sure. 

Items  103  to  117. — Weight  of  Steam  present  at  the  Several  Events  of 
the  Stroke  is  the  result  obtained  by  the  formula 


where  w=the  weight  in  pounds,  v  =  the  per 
cent  of  stroke  plus  clearance  per  cent  multi- 
plied into  the  cylinder  volume,  and  s  =  the 
volume  of  one  pound  of  steam  at  the  pressure 
above  atmosphere  as  measured  on  the  card. 

Items  118  to  122. — Indicated  Horse-power  from  the  Card  Measure- 
ments. 

Item  123. — Steam  per  I.  H.  P.  per  Hour = Item  28 -I  tern  122. 
Item  124. — Steam  per  I.  H.  P.  per  Hour  by  Indicator  =  (Item  112  — 

Item  117)Xltem  llX60-r-Item  122. 

Item  125.— Dry  Coal  per  I.  H.  P.  per  Hour=Item  35^Item  122. 
Item  126. — Weight  of  Steam  per  Revolution  by  Tank = Item  26-f- 

Item  10. 
Item  127. — Weight  of  Mixture  in  Cylinder  per  Re  volution = Item  126 

+Item  117. 
Item  128. — Per  Cent  of  Mixture  present  as  Steam  at  Cut-off = Item 

107 -i- Item  127. 
Item  129. — Per  Cent  of  Mixture  present  as  Steam  at  Release = Item 

112 -Item  127. 
Item  130. — Reevaporation    per    Re  volution = Item    112— Item   107^ 

when  Item  1 12  >  Item  107. 
Item  131. — Condensation  per  Revolution=Item  107— Item  112,  when 

Item  107  >  Item  112. 
Item  132. — Reevaporation  per  I.  H.  P.  per  Hour = Item   130  X Item 

11 X  60  H- I  tern  122. 

Item  133. — Condensation  per  I.  H.  P.  per  Hour  =  Item  131 X  Item. 
11X60^  Item  122. 


80  LOCOMOTIVE  PERFORMANCE. 

Item  134.— Draw-bar  Pull   Equivalent  to  Average  M.   E.   P.     The 

D.  H.  P.  =draw-bar  pull X. 0004956 XR.  P.  M. 

and 
I.  H.  P.  =  average  M.  E.  P.X.0542XR.  P.  M. 

Assumed  that  all  the  I.  H.  P.  was  transmitted  to  the 
draw-bar  without  friction  losses.  Then,  these  expres- 
sions are  equal  and  their  second  terms  may  be  equated. 
Performing  the  operation  indicated  and  solving  will 
give  Draw-bar  pull=M.  E.  P.X  109.419.  Item  134 
therefore  =  Item  102X109.419.  It  was  found  imprac- 
ticable to  get  the  correct  observed  value  of  draw- 
bar stress,  and  therefore  it  was  assumed  that  at  equal 
cut-offs,  friction  was  constant  at  all  speeds.  (See  Chap- 
ter XIX.)  Items  135  •  to  139  are  computed  on  this 
basis. 

Item  135. — Friction  Expressed  as  M.  E.  P.  is  assumed  constant  for 
all  tests  at  same  cut-off. 

Item  136. — Friction  Expressed  as  Draw-bar  Pull  =  Item  135X109.419. 

Item  137. — Assumed  Friction  Horse-power  =  Item  135 X. 0542 X Item 
11. 

Item  138.— Draw-bar  Horse-power=Item  122 -Item  137. 

Item  139. — Mechanical  Efficiency = I  tern  138-=- 1  tern  122. 

Item  140.— I.  H.  P.  per  Square  Foot  Heating  Surf  ace = Item  122  H- 
1214.4. 

Item  141.— I.  H.  P.  per  Square  Foot  of  Grate  Surface  =  I  tern  122 -f- 
17.25. 

Item  142. — Steam  Used  per  Dynamometer  Horse-power  per  Hour  = 
Item  28-7-  I  tern  138. 

Item  143.— Coal  Used  per  D.  H.  P.  per  Hour  =  Item  35 -v- Item  138. 

Item  144. — B.  T.  U.  Used  by  Engine  per  Minute = I  tern  28  X  Item 
40-60. 

Item  145.— B.  T.  U.  Used  by  Engine  per  I.  H.  P.  per  Minute  =  Item 
144 -Item  122. 

Item  146.— B.  T.  U.  Used  by  Engine  per  D.  H.  P.  per  Minute = Item 
144 -I  tern  138. 

Item  147.— Coal  Used  per  Mile  Run  =  Item  32-Item  12. 

Item  148.— D.  H.  P.  per  Square  Foot  Heating  Surface  =  Item  138-7- 
1214.4. 


METHOD  OF  TESTING  AND  DATA.  81 

Item  149.— D.  H.  P.  per  Square  Foot  Grate  Surf  ace = I  tern  138-=- 

17.25. 
Item  150. — Water  Evaporated  from  and    at    212°  F.   per   Hour  = 

Item  47. 
Item  151. — Coal  fired  per  Hour  = 

Item  150 


10.08-. 000244  X  Item  150' 

Item  152. — Coal  burned  per  Square  Foot  of  Grate  per  Hour = Item 

151^  17.25. 

Item  153.— Water  per  Pound  of  Coal=Item  27-r-Item  151. 
Item  154. — Equivalent  Evaporation  per  Pound  of  Coal = Item  150 -r- 

Item  151. 

Item  155.— Coal  per  I.  H.  P.  per  Hour  =  Item  151 -Item  122. 
Item  156.— Coal  per  D.  H.  P.  per  Hour  =  Item  151 -Item  138. 
Item  157.— B.  T.  U.  Taken  up  by  Boiler  per  Pound  of  Coal= 

Item  40Xltem  153. 

Table  XIX.,  of  Locomotive  Performance  based  on  uniform  firing 
conditions,  is  composed  of  several  items  so  corrected  as  to  eliminate 
the  effect  of  irregularities  in  firing.  In  this  one  table  the  total 
weight  of  coal  fired  per  hour,  which  is  a  factor  in  all  these  items, 
is  not  that  which  was  found  by  experiment,  but  was  calculated 
from  the  known  weight  of  water  evaporated  per  hour  by  use  of 
the  formula 

c  w 


10.08  -. 000244  JF' 

where  C  is  the  pounds  of  coal  fired  per  hour,  and  W  is  the  total 
pounds  of  water  evaporated  from  and  at  212°  per  hour.  The 
significance  of  this  formula  has  been  developed  in  the  following  chap- 
ter, pages  150  and  151.  For  the  purposes  of  this  table,  W,  Item  153, 
was  taken  from  the  experimental  results,  and  C,  Item  151,  computed. 
Items  151  to  155  are  calculated,  using  the  value  C  instead  of  the  ex- 
perimental results. 

The  coal  used  in  these  tests  was  the  same  throughout,  namely, 
Indiana  block  from  the  Brazil  field,  a  light  fuel  which  burns  freely 
to  a  fine  ash.  The  following  is  the  average  result  of  four  analyses: 


82  LOCOMOTIVE  PERFORMANCE. 

Per  cent  fixed  carbon 51.06 

Per  cent  volatile  matter 39.26 

Per  cent  combined  moisture 3.14 

Per  cent  ash. .  6.54 


Total 100.00 

B.  T.  U.  per  pound  of  dry  coal 13,000 

It  has  been  shown  by  tests  made  subsequent  to  those  herein  discussed 
that  0.8  of  a  pound  of  first-class  Pittsburg  or  West  Virginia  coal  will 
give  in  locomotive  service  approximately  the  same  results  as  one 
pound  of  Brazil  block. 

The  record  of  the  observed  and  calculated  results  is  as  follows: 


METHOD  OF  TESTING  AND  DATA. 


83 


TABLE  I. 
GENERAL  CONDITIONS. 


Valve 

T)n-rn 

Setting 

Approx- 

Reverse- 

Labora- 
tory 
Symbol. 

Date. 

.L'lira- 
tion  of 
Test, 
Min- 

and 
Propor- 
tions 
(SPP 

imate 
Cut-off, 
Per  Cent 
of 

lever 
Notch 
Forward 
of 

Throttle 
Position.' 

Draw- 
bar 
Pull. 

1 

utes. 

V.occ 

Con- 

Stroke. 

Center. 

stants). 

fc 

1 

2 

3 

4 

5 

6 

7 

8 

9 

1 

15-1&-V 

Nov.    23,  '94 

190 

I 

25 

1st 

Fully  open 

4227 

2 

25-1-V 

Nov.    26,  '94 

240 

I 

25 

1st 

Fully  open  !  3657 

3 

35-1-V 

Dec.       4,  '94 

140 

I 

25 

1st 

Fully  open  j  2796 

4 

55-1-V 

Dec.     18,  '95 

120 

I 

25 

1st 

Fully  open  j  1544 

5 

15-1-A 

Dec.     12,  '94 

240 

II 

25 

1st 

Fully  open 

4180 

6 

25-1-A 

Dec.     14,  '94 

255 

II 

25 

1st 

Fully  open 

2893 

7 

35-1-A 

Dec.     17,  '94 

180 

II 

25 

1st 

Fully  open 

2600 

8 

45-1-A 

Nov.    20,  '95 

150 

II 

25 

1st 

Fully  open 

1870 

9 

55-1-A 

Nov.    25,  '95 

120 

II 

25 

1st 

Fully  open 

1342 

10 

15-2-  A 

Nov.    13,  '95 

180 

II 

35 

2d 

Fully  open 

6409 

11 

25-2-A 

Oct.     25,  '95 

180 

II 

35 

2d 

Fully  open 

5259 

12 

35-2-A 

Dec.     19,  '94 

180 

II 

35 

2d 

Fully  open 

4157 

13 

45-2-A 

Nov.     18,  '95 

140 

n 

35 

2d 

Fully  open 

3132 

14 

55-2-A 

Nov.    22,  '95 

68 

ii 

35 

2d 

Fully  open 

2431 

15 

25-3-A 

Nov.      1,  '95 

122.5 

n 

45 

3d 

Fully  open 

6666 

16 

35-3-A 

Nov.     15,  '95 

120 

ii 

45 

3d 

Fully  open 

5050 

17 

15-9  -A 

Nov.      6,  '96 

150 

ii 

80 

9th 

Partly  open 

7224 

18 

35-2-B 

Jan.      14,  '95 

170 

in 

35 

2d 

Fully  open 

2756 

19 

35-2-C 

Jan.     23,  '95 

120 

IV 

35 

2d 

Fully  open 

5100 

20 

35-2-E 

Jan.      16,  '95 

180 

V 

35 

2d 

Partly  open 

2722 

21 

35-2-F 

Jan.     21,  '95 

180 

VI 

35 

2d 

Partly  open  <  2851 

22 

15-1-G 

Nov.      9,  '96 

180 

VII 

25 

1st 

Fully  open  :  4704 

23 

35-1-G 

Nov.    20,  '96 

170 

VII 

25 

1st 

Fully  open     2860 

24 

35-l6-G 

Dec.       2,  '96 

170 

VII 

25 

1st 

Fully  open     2903 

25 

55-1-G 

Nov.    23,  '96 

120 

VII 

25 

1st 

Fully  open     1796 

26 

35-2-G 

Nov.     13,  '96 

160 

VII 

35 

2d 

Fully  open 

4467 

27 

35-3-G 

Dec.       4,  '96 

140 

VII 

45 

3d 

Partly  open 

3423 

28 

15-9-G 

Nov.     12,  '96 

160 

VII 

80 

9th 

Partly  open 

7473 

29 

15-1-H 

Dec.       9,  '96 

180 

VIII 

25 

1st 

Fully  op  zn 

4418 

30 

35-1-H 

Dec.     18,  '96 

160 

VIII 

25 

1st 

Fully  open 

2857 

31 

55-1-H 

Feb.     11,  '97 

120 

VIII 

25 

1st 

Fully  open 

1783 

32 

35-2-H 

Dec.     16,  '96 

120 

VIII 

35 

2d 

Fully  open 

3833 

33 

35-26-H 

Feb.     10,  '97 

160 

VIII 

35 

2d 

Partly  open 

2857 

34 

35-3-H 

Dec.     14,  '96 

120 

VIII 

45 

3d 

Partly  open 

3316 

35 

15-9-H 

Dec.     11,  '96 

180 

VIII 

80 

9th 

Partly  open 

7114 

36 

15-1-1 

March  27,  '97 

270 

IX 

25 

1st 

Fully  open 

37 

35-1-1 

March  29,  '97 

170 

IX 

25 

1st 

Fully  open 

38 

55-1-1 

April      1,  '97 

120 

IX 

25 

1st 

Fully  open 

39 

15-9-1 

March  26,  '97 

190 

IX 

80 

9th 

Partly  open 

40 

15-4^T 

April    14,  '97 

300 

X 

25 

4th 

Fully  open 

41 

35-4-J 

April    13,  '97 

180 

X 

25 

4th 

Fully  open 

42 

15-15-J 

April      9,  '97 

160 

X 

80 

15th 

Partly  open 

43 

15-2-K 

April    27,  '97 

300 

XI 

35 

2d 

Fully  open 

44 

35-2-K 

April    24,  '97 

180 

XI 

35 

2d 

Fully  open 

i 

LOCOMOTIVE  PERFORMANCE. 


TABLE  II. 

GENERAL   CONDITIONS— Continued. 


Speed. 

Temperature,  Degrees  F. 

Labora- 

Miles 

1 

tory 
Symbol. 

Total 
Revolu- 
tions. 

Revolu- 
tions 
per 
Minute. 

Run 
Equiva- 
lent to 
Total 
Revolu- 

Miles 
Hour. 

Feed- 
water. 

Labora- 
tory. 

Smoke- 
box. 

£ 

tions. 

1 

2 

10 

11 

12 

13 

14 

15 

16 

1 

15-16-V 

14,891 

78.37 

46.12 

14.56 

53.76 

73.93 

549.50 

2 

25-1-V 

29,174 

121.56 

90.36 

22.59 

53.85 

69.62 

605.60 

3 

35-1-V 

26,111 

186.51 

80.88 

34.66 

51.90 

69.00 

633.00 

4 

55-1-V 

36,080 

300.67 

111.75 

55.88 

58.10 

75.70 

666.60 

6 

15-1-A 

19,367 

80.69 

59.99 

15.00 

53.20 

65.46 

553.20 

6 

25-1-A 

33,024 

129.50 

102.29 

24.07 

53.75 

67.34 

567.0 

7 

35-1-A 

34,373 

190.96 

106.47 

35.49 

53.17 

74.91 

628.10 

8 

45-1-A 

37,359 

249.06 

115.71 

46.29 

56.40 

75.60 

644.30 

9 

55-1-A 

36,693 

305.75 

113.65 

56.83 

56.00 

75.90 

675.40 

10 

15-2-  A 

13,878 

77.10 

42.98 

14.33 

55.19 

79.30 

620.60 

11 

25-2-A 

22,973 

127.63 

71.15 

23.72 

56.00 

84.80 

696.30 

12 

35-2-A 

34,204 

190.02 

105.94 

35.31 

52.54 

72.20 

720.30 

13 

45-2-A 

34,454 

246.10 

106.72 

45.74 

55.00 

83.70 

740.50 

14 

55-2-A 

20,808 

306.00 

64.45 

56.87 

58.40 

76.40 

754.60 

15 

25-3-A 

15,819 

129.10 

49.00 

24.00 

53.30 

76.40 

762.10 

16 

35-3-A 

22,054 

183.78 

68.31 

34.15 

55.50 

76.70 

798.10 

17 

15-9-  A 

11,886 

79.24 

36.82 

14.73 

55.62 

78.50 

724.20 

18 

35-2-B 

32,029 

188.41 

99.20 

35.01 

50.00 

65.90 

664.30 

19 

35-2-C 

22,746 

189.55 

70.45 

35.23 

51.68 

70.80 

737.70 

20 

35-2-E 

34,947 

194.15 

108.24 

36.08 

51.88 

70.60 

652.00 

21 

35-2-F 

33,673 

187.07 

104.30 

34.76 

52.72 

71.50 

653.10 

22 

15-1-G 

14,589 

81.05 

45.18 

15.06 

53.33 

68.70 

582.50 

23 

35-1-G 

32,361 

190.36 

100.23 

35.38 

55.00 

74.40 

684.70 

24 

35-l6-G 

32,341 

190.24 

100.17 

35.35 

52.47 

77.60 

618.30 

25 

55-1-G 

36,300 

302.50 

112.43 

56.22 

54.17 

79.40 

26 

35-2-G 

29,952 

187.20 

92.77 

34.80 

53.55 

77.90 

654.50 

27 

35-3-G 

26,612 

190.09 

82.43 

35.33 

52.62 

69.60 

719.00 

28 

15-9-G 

12,619 

78.87 

39.08 

14.66 

53.13 

77.40 

724.00 

29 

15-1-H 

14,660 

81.44 

45.41 

15.14 

54.63 

71.50 

570.00 

30 

35-1-H 

30,397 

189.98 

94.15 

35.31 

52.59 

67.10 

655.00 

31 

55-1-H 

35,308 

294.23 

109.36 

54.68 

52.08 

70.60 

695.00 

32 

35-2-H 

23,183 

193.19 

71.81 

35.90 

53.01 

71.80 

33 

35-26-H 

30,653 

191.58 

94.94 

35.60 

50.56 

74.30 

689.20 

34 

35-3-H 

23,289 

194.07 

72.13 

36.07 

53.00 

73.50 

35 

15-9-H 

14,421 

80.12 

44.67 

14.89 

53.22 

81.10 

695.70 

36 

15-1-1 

21,853 

80.93 

67.69 

15.04 

52.80 

66.40 

37 

35-1-1 

32,444 

190.84 

100.49 

35.47 

56.30 

74.50 

38 

55-1-1 

34,868 

290.57 

108.00 

54.00 

54.50 

79.50 

39 

15-9-1 

15,067 

79.30 

46.67 

14.73 

51.90 

68.00 

40 

15-4-J 

24,934 

83.11 

77.23 

15.45 

53.77 

41 

35-4^1 

34,308 

190.60 

106.26 

35.42 

54.00 

42 

15-15-J 

12,987 

81.17 

40.23 

14.62 

51.10 

43 

15-2-K 

24,671 

82.24 

76.41 

15.28 

56.00 

44 

35-2-K 

33,722 

180.73 

104.45 

34.82 

56.00 

METHOD  OF   TESTING  AND  DATA. 


85 


TABLE  III. 

GENERAL  CONDITIONS— Continued. 


Pressures,  Pounds  per  Square  Inch. 

Injectors. 

Labora- 

Draft, 
Inches 

Number. 

tory 
Symbol. 

Boiler 
by 
Gauge. 

Atmos- 
phere by 
Barom- 
eter. 

Absolute 
Boiler. 

Dry 

Pipe 
by 
Gauge. 

Times 
Started. 

Minutes 
One  or 
Both  in 
Action. 

of 
Water.* 

1 

1 

2 

17 

18 

19 

20 

21 

22 

23 

15-16-V 

127.27 

14.54 

141.8 

130.00 

14 

129 

2.04 

2 

25-1-V 

127.12 

14.34 

141.4 

130.40 

7 

213 

2.60 

3 

35-1-V 

128.87 

14.32 

143.2 

127.20 

1 

136 

3.43 

4 

55-1-V 

128.40 

14.38 

142.8 

123.04 

1 

120 

3.20 

5 

15-1-A 

125.94 

14.46 

140.4 

124.58 

22 

130 

1.72 

6 

25-1-A 

120.04 

14.52 

134.6 

113.37 

10 

236 

1.93 

7 

35-1-A 

129.72 

14.62 

144.3 

127.23 

2 

180 

3.00 

8 

45-1-A 

128.84 

14.31 

143.1 

124.90 

2 

146 

2.68 

9 

55-1-A 

124.91 

14.18 

139.1 

121.29 

1 

120 

2.58 

10 

15-2-  A 

129.48 

14.39 

143.9 

125.10 

9 

149 

2.42 

11 

25-2-A 

129.32 

14.35 

143.7 

124.90 

180 

3.37 

12 

35-2-A 

131.65 

14.49 

146.1 

120.67 

180 

4.42 

13 

45-2-A 

126.67 

14.29 

141.0 

122.10 

140 

4.93 

14 

55-2-A 

124.00 

14.43 

138.4 

118.80 

68.5 

4.58 

15 

25-3-A 

127.19 

14.47 

141.7 

123.20 

122.5 

5.45 

16 

35-3-A 

125.28 

14.34 

139.6 

122.08 

120 

7.49 

17 

15-9-  A 

122.47 

14.34 

136.8 

74.17 

150 

4.56 

18 

35-2-B 

98.36 

14.39 

112.8 

95.57 

8 

158 

3.28 

19 

35-2-C 

143.28 

14.42 

157.7 

143.08 

3 

125 

5.13 

20 

35-2-E 

128.05 

14.49 

142.6 

95.46 

3 

175 

2.89 

21 

35-2-F 

155.35 

14.68 

170.1 

93.11 

9 

149 

2.57 

22 

15-1-G 

123.58 

14.39 

138.0 

120.54 

12 

127 

1.87 

23 

35-1-G 

125.00 

14.55 

139.6 

123.91 

1 

170 

3.02 

24 

35-1&-G 

128.23 

14.56 

142.8 

126.44 

1 

170 

2.98 

25 

55-1-G 

126.90 

14.46 

141.4 

123.18 

1 

120 

3.57 

26 

35-2-G 

121.04 

14.54 

135.5 

118.34 

1 

160 

4.65 

27 

35-3-G 

125.93 

14.34 

140.2 

86.62 

140 

4.88 

28 

15_9_G 

124.06 

14.49 

138.6 

76.33 

154 

4.76 

29 

15-1-H 

123.55 

14.32 

137.9 

119.97 

126 

1.93 

30 

35-1-H 

121.16 

14.57 

135.8 

117.09 

160 

3.00 

31 

55-1-H 

127.48 

14.39 

141.9 

121.52 

120 

3.44 

32 

35-2-H 

112.04 

14.58 

126.6 

108.36 

115 

4.33 

33 

35-26-H 

122.64 

14.54 

137.1 

92.97 

160 

3.18 

34 

35-3-H 

116.48 

14.29 

130.8 

74.52 

120 

4.52 

35 

15-9-H 

122.72 

14.37 

137.1 

73.94 

180 

4.99 

36 

15-1-1 

127.95 

14.53 

142.5 

124.43 

37 

35-1-1 

128.05 

14.45 

142.5 

124.97 

38 

55-1-1 

125.43 

14.47 

139.9 

122.90 

39 

15-9-1 

131.61 

14.35 

145.9 

72.91 

40 

15_4_J 

127.51 

14.50 

142.0 

126.49 

41 

35-4-J 

131.95 

14.42 

146.4 

124.05 

42 

15-15^1 

128.94 

14.41 

143.3 

89.61 

43 

15-2-K 

125.50 

14.21 

139.7 

123.31 

44 

35-2-K 

126.02 

14.15 

140.2 

124.57 

*  Multiply  these  values  by  1.3  to  obtain  draft  at  point  of  maximum  draft  (in  front  of  dia- 
phragm). 


LOCOMOTIVE  PERFORMANCE. 


TABLE  IV. 

BOILER  PERFORMANCE. 

WATER  AND  STEAM. 


1 

Labora- 
tory    . 
Symbol. 

Water 
Delivered 
to  Boiler 
and  Pre- 
sumably 
Evap- 
orated. 

Water 
Lost 
from 
Boiler. 

Steam 
Supplied 
to 
Engine. 

Water 
Evapor- 
ated by 
Boiler 

Hour. 

Steam 
Used  by 
Engine 

Hour. 

Quality 
of 
Steam 
in 
Dome. 
Mois- 
ture. 

Water  Evap- 
orated per  Hour 
per  Square 
Foot  of 

Heating 
Surface. 

Grate 
Sur- 
face. 

g 

Per 

fc 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

Cent. 

Lbs. 

Lbs. 

1 

2 

24 

25 

36 

27 

28 

29 

30 

31 

i 

15-VV 

17,789.6 

67.6 

17,721.0 

5,617.8 

5,596.4 

.63 

4.626 

325 

2 

25-1-V 

29,475.7 

82.3 

29,393.4 

7,368.9 

7,348.4 

.68 

6.068 

427 

3 

35-1-V 

19,899.2 

48.6 

19,850.6 

8,528.2 

8,507.4 

.63 

7.022 

494 

4 

55-1-V 

19,418.4 

41.6 

19,376.8 

9,709.2 

9,688.4 

.88 

7.995 

563 

5 

15-1-A 

22,100.2 

81.6 

22,018.6 

5,525.1 

5,504.7 

.49 

4.549 

320 

6 

25-1-A 

25,894.6 

84.5 

25,810.1 

6,092.8 

6,072.9 

.78 

5.017 

353 

7 

35-1-A 

24,367.5 

62.8 

24,304.7 

8,122.5 

8,101.6 

.83 

6.688 

471 

8 

45-1-A 

21,672.6 

51.7 

21,620.9 

8,669.0 

8,648.3 

.87 

7.138 

502 

9 

55-1-A 

17,882.6 

40.6 

17,842.0 

8,941.3 

8,921.0 

1.22 

7.363 

518 

10 

15-2-A 

21,840.6 

62.7 

21,777.9 

7,280.2 

7,259.3 

.76 

5.995 

422 

11 

25-2-A 

28,906.0 

62.7 

28,843.3 

9,635.3 

9,614.4 

.90 

7.934 

558 

12 

35-2-A 

34,324.5 

64.0 

34,260.5 

11,441.5 

11,420.2 

.06 

9.422 

663 

13 

45-2-A 

29,100.4 

47.7 

29,052.7 

12,471.0 

12,451.2 

.24 

10.269 

722 

14 

55-2-A 

15,911.4 

22.9 

15,888.5 

14,039.5 

14,019.2 

.13 

11.561 

813 

15 

25-3-A 

26,401.0 

41.8 

26,359.2 

12,931.1 

12,910.6 

.11 

10.648 

749 

16 

35-3-A 

29,874.8 

40.6 

29,834.2 

14,937.4 

14,917.1 

.11 

12.300 

865 

17 

15-9-A 

28,522.0 

50.0 

28,472.0 

11,408.8 

11,388.8 

.94 

9.395 

661 

18 

35-2-B 

24,554.7 

46.5 

24,508.2 

8,666.3 

8,649.9 

.69 

7.136 

502 

19 

35-2-C 

26,008.5 

45.6 

25,962.9 

13,004.2 

12,981.3 

.70 

10.708 

754 

20 

35-2  -E 

25,696.7 

62.1 

25,634.6 

8,565.6 

8,544.9 

.68 

7.053 

496 

21 

35-2-F 

24,333.3 

74.1 

24,259.2 

8,111.1 

8,086.4 

1.00 

6.679 

470 

22 

15-1-G 

18,695.7 

60.3 

18,635.4 

6,231.9 

6,211.8 

1.06 

5.132 

361 

23 

35-1-G 

26,562.7 

57.5 

26,505.2 

9,375.1 

9,354.8 

1.14 

7.720 

543 

24 

35-l6-G 

26,743.3 

58.9 

26,684.4 

9,438.8 

9,418.0 

.40 

7.772 

547 

25 

55-1-G 

20,760.9 

41.0 

20,719.9 

10,380.4 

10,359.9 

.31 

8.548 

602 

26 

35-2-G 

32,846.0 

52.8 

32,793.2 

12,317.3 

12,297.4 

.44 

10.143 

714 

27 

35-3-G 

27,060.2 

47.6 

27,012.6 

11,597.2 

11,576.8 

.62 

9.550 

675 

28 

15-9-G 

30,872.4 

55.7 

30,816.7 

11,577.1 

11,556.2 

.29 

9.533 

671 

29 

15-1-H 

18,223.4 

60.3 

18,163.1 

6,074.5 

6,054.4 

.62 

5.002 

351 

30 

35-1-H 

24,723.3 

52.8 

24,670.8 

9,271.2 

9,251.4 

.49 

7.634 

537 

31 

55-1-H 

20,513.6 

41.0 

20,472.6 

10,256.6 

10,236.3 

.29 

8.446 

595 

32 

35-2-H 

24,733.3 

36.8 

24,696.5 

12,366.6 

12,348.2 

.34 

10.183 

717 

33 

35-2&-H 

25,829.0 

50.7 

25,778.3 

9,685.9 

9,666.9 

.20 

7.976 

561 

34 

35-3-H 

23,385.7 

38.2 

23,347.5 

11,692.9 

11,673.8 

.27 

9.628 

677 

35 

15-9-H 

34,373.4 

60.3 

34,313.1 

11,457.8 

11,437.7 

.29 

9.435 

664 

36 

15-1-1 

27,608.3 

93.6 

27,514.7 

6,135.2 

6,114.4 

5.052 

356 

37 

35-1-1 

26,781.0 

58.8 

26,722.2 

9,453.2 

9,432.5 

7.780 

548 

38 

55-1-1 

22,509.0 

40.6 

22,468.4 

11,254.5 

11,234.2 

9.268 

652 

39 

15-9-1 

34,374.3 

67.1 

34,307.2 

10,857.3 

10,836.1 

8.940 

630 

40 

15-4-J 

32,783.5 

102.8 

32,680.8 

6,556.7 

6,536.2 

5.390 

380 

41 

35-4-J 

30,646.7 

63.6 

30,583.1 

10,215.6 

10,194.4 

8.413 

592 

42 

15-15-J 

30,879.1 

57.5 

30,821.6 

11,608.7 

'11,587.0 

9.558 

673 

43 

15-2-K 

33,443.0 

101.0 

33,451.0 

6,710.4 

6,690.2 

5.525 

388 

44 

35-2-K 

30,934.0 

61.2 

30,872.8 

10,311.3 

10,290.9 

8.490 

597 

METHOD  OF  TESTING  AND  DATA. 


87 


TABLE  V. 

BOILER  PERFORMANCE— Continued. 
COAL  CONSUMPTION — BRAZIL  BLOCK  COAL. 


Total             Dl7 

Dry 
Cinders 

Dry 

i"*rt_l 

Combus- 
tible 

Dry  Coat  Fired  per 
Hour  per  Square 
Foot  of 

Labora- 

Dry 
Coal 

Asn 
Caught 

Caught 
in 

Coal 
Fired 

Fired 
per 

J5 

tory 
Symbol. 

Fired.* 

in 
Ashpan. 

Smoke- 
box. 

per 
Hour.* 

Hour  by 
Analysis. 

Heating 
Surface.* 

Grate 
Surface.* 

a 

3 
* 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

1 

2 

32 

33 

34 

35 

36 

37 

38 

1 

15-VV 

2,577.2 

261.5 

31.0 

813.9 

732 

.670 

47.2 

2 

25-1-V 

4,460.0 

320.0 

79.5 

1,115.0 

1,003 

.918 

64.6 

3 

35-1-V 

3,180.0 

272.0 

124.5 

1,362.9 

1,227 

1.122 

78.9 

4 

55-1-V 

3,330.0 

238.5 

255.0 

1,665.0 

1,498 

1.371 

96.5 

5 

15-1-A 

3,399.0 

292.0 

57.0 

849.7 

765 

.700 

49.3 

6 

25-1-A 

3,864.3 

93.5 

60.0 

909.2 

818 

.748 

52.8 

7 

35-1-A 

3,784.9 

299.0 

135.0 

1,261.6 

1,135 

1.038 

73.1 

8 

45-1-A 

3,272.2 

231.5 

135.7 

1,308.9 

1,178 

1.078 

75.9 

9 

55-1-A 

2,980.3 

219.5 

162.0 

1,490.2 

1,341 

1.227 

86.4 

10 

15-2-  A 

3,296.7 

257.5 

71.0 

1,098.9 

989 

.905 

63.7 

11 

25-2-A 

4,826.0 

25.0 

227.0 

1,608.7 

1,448 

1.324 

93.3 

12 

35-2-A 

5,932.9 

257.5 

239.0 

1,977.6 

1,780 

1.628 

114.6 

13 

45-2-A 

5,720.2 

242.5 

380.5 

2,451.5 

2,206 

2.019 

142.1 

14 

55-2-A 

2,994.8 

205.0 

330.0 

2,642.5 

2,378 

2.176 

153.2 

15 

25-3-A 

4,684.1 

91.0 

231.0 

2,294.3 

2,065 

1.889 

133.0 

16 

35-3-A 

6,266.3 

298.0 

118.2 

3,133.2 

2,819 

2.581 

181.6 

17 

15-9-  A 

5,014.0 

265.0 

174.0 

2,005.6 

,805 

1.651 

116.3 

18 

35-2-B 

4,369.7 

460.5 

177.5 

1,542.2 

,388 

1.270 

89.4 

19 

35-2-C 

5,356.1 

384.0 

348.0 

2,678.1 

2,410 

2.205 

155.3 

20 

35-2-E 

4,106.5 

353.0 

113.5 

,368.8 

,232 

1.127 

79.3 

21 

35-2-F 

3,859.1 

294.5 

109.5 

,286.3 

,158 

1.059 

74.6 

22 

15-1-G 

2,678.0 

262.0 

43.0 

892.7 

803 

.735 

51.8 

23 

35-1-G 

4,288.4 

341.5 

141.5 

,518.1 

,362 

.246 

87.7 

24 

35-1&-G 

4,150.3 

380.0 

179.0 

,464.8 

,318 

.206 

84.9 

25 

55-1-G 

3,768.9 

241.0 

314.5 

,884.5 

,696 

.552 

109.2 

26 

35-2-G 

6,182.7 

363.0 

168.5 

2,318.5 

2,087 

.909 

134.4 

27 

35-3-G 

4,707.9 

365.0 

157.0 

2,017.7 

,816 

.662 

117.0 

28 

15-9-G 

5,486.7 

354.0 

168.0 

2,057.5 

,852 

.694 

119.3 

29 

15-1-H 

2,374.5 

240.0 

37.0 

791.5 

713 

.652 

45.9 

30 

35-1-H 

4,152.3 

320.0 

169.0 

1,557.1 

1,401 

.283 

90.3 

31 

55-1-H 

3,203.1 

213.5 

233.5 

1,601.6 

1,441 

.319 

92.8 

32 

35-2-H 

4,250.3 

297.0 

204.0 

2,125.1 

1,912 

.750 

123.2 

33 

35-2&-H 

4,321.2 

331.5 

100.5 

1,620.4 

1,458 

.334 

93.9 

34 

35-3-H 

4,248.3 

346.0 

300.0 

2,124.1 

1,912 

.749 

123.2 

35 

15-9-H 

6,363.1 

344.0 

234.0 

2,121.0 

1,909 

1.746 

123.0 

36 

15-1-1 

37 

35-1-1 

38 

55-1-1 

39 

15-9-1 

40 

15-4^1 

41 

35-4-J 

42 

15-15-J 

43 

15-2-K 

44 

35-2-K 

*  To  obtain  an  approximate  measure  of  boiler  performance  in  terms  of  West  Virginia  or 
Pittsburgh  coal,  multiply  the  value  of  the  columns  32,  35,  37.  and  38  by  0.8. 


88 


LOCOMOTIVE  PERFORMANCE. 


TABLE  VI. 

BOILER  PERFORMANCE— Continued. 


B.  T.  U.—  Taken  Up  by 

Actual  Water 

Evaporated 

Quality 

Labora- 

of Steam 

tory 

in  Dome, 

Each 

Boiler 

Boiler 

Pei^ 

Per 

tl 

Symbol. 

Moisture. 

Pound 

Boiler 

per 

per 

Pound 

Pound 

1 

of 

per 

Pound 

Pound 

of  Coal.* 

Combusti- 

Water. 

Minute. 

of  Coal. 

Combus- 

ble. 

3 

tible. 

fe 

Per  Cent. 

Lbs. 

Lbs. 

1 

2 

39 

40 

41 

43 

43 

44 

45 

1 

15-16-V 

0.63 

1,162.6 

108,858 

8,026 

8,918 

6.903. 

7.670 

2 

25-1-V 

0.68 

1,161.8 

142,688 

7,678 

8,531 

6.609 

7.343 

3 

35-1-V 

0.63 

1,164.7 

165,543 

7,288 

8,098 

6.258 

6.953 

4 

55-1-V 

0.88 

1,156.3 

187,109 

6,743 

7,492 

5.831 

6.479 

5 

15-1-A 

0.49 

1,164.1 

107,194 

7,569 

8,410 

6.502 

7.224 

6 

25-1-A 

0.78 

,160.0 

117,798 

7,771 

8,638 

6.701 

7.434 

7 

35-1-A 

0.83 

,161.7 

157,268 

7,479 

8,310 

6.438 

7.153 

8 

45-1-A 

0.87 

,158.1 

167,336 

7,671 

8,523 

6.623 

7.379 

9 

55-1-A 

1.22 

,154.7 

172,079 

6,929 

7,699 

6.000 

6.666 

10 

15-2-A 

0.76 

,160.2 

140,778 

7,686 

8,541 

6.625 

7.361 

11 

25-2-A 

0.90 

,158.2 

185,994 

6,937 

7,709 

5.990 

6.633 

12 

35-2-A 

.06 

,159.3 

221,072 

6,707 

7,452 

5.786 

6.429 

13 

45-2-A 

.24 

,155.9 

240,262 

5,881 

6,534 

5.087 

5.652 

14 

55-2-A 

.13 

,153.9 

269,996 

6,130 

6,812 

5.313 

5.903 

15 

25-3-A 

.11 

,158.8 

249,743 

6,531 

7,256 

5.636 

6.262 

16 

35-3-A 

.11 

,156.3 

287,871 

5,513 

6,126 

4.768 

5.296 

17 

15-9-A 

0.94 

,157.2 

220,038 

6,583 

7,314 

5.688 

6.320 

18 

35-2-B 

0.69 

,160.5 

167,624 

6,521 

7,245 

5.619 

6.243 

19 

35-2-C 

0.70 

,166.7 

252,873 

5,666 

6,296 

4.856 

5.395 

20 

35-2-E 

0.68 

,164.1 

166,188 

7,283 

8,093 

6.258 

6.953 

21 

35-2-F 

.00 

,165.1 

157,502 

7,348 

8,163 

6.305 

7.005 

22 

15-1-G 

.06 

,158.6 

120,340 

8,088 

8,988 

6.981 

7.756 

23 

35-1-G 

.14 

,156.5 

180,706 

7,164 

7,961 

6.194 

6.882 

24 

35-l6-G 

.40 

,157.4 

182,072 

7,458 

8,287 

6.444 

7.160 

25 

55-1-G 

.31 

,156.1 

200,015 

6,369 

7,076 

5.508 

6.120 

26 

35-2-G 

.44 

,154.6 

237,025 

6,134 

6,815 

5.313 

5.903 

27 

35-3-G 

.62 

,154.8 

223,206 

6,637 

7,375 

5.748 

6.386 

28 

15-9-G 

.29 

,157.0 

223,243 

6,510 

7,234 

5.627 

6.252 

29 

15-1-H 

.62 

,152.4 

116,668 

8,842 

9,823 

7.675 

8.528 

30 

35-1-H 

.49 

,155.3 

178,516 

6,879 

7,643 

5.954 

6.615 

31 

55-1-H 

.29 

,158.5 

198,046 

7,419 

8,243 

6.404 

7.115 

32 

35-2-H 

.34 

,153.5 

237,746 

6,713 

7,459 

5.819 

6.465 

33 

35-2&-H 

.20 

,160.0 

187,260 

6,934 

7,704 

5.977 

6.641 

34 

35-3-H 

.27 

,155.9 

225,266 

6,366 

7,071 

5.505 

6.116 

35 

15-9-H 

.29 

,156.6 

220,866 

6,248 

6,942 

5.402 

6.002 

36 

15-1-1 

37 

35-1-1 

38 

55-1-1 

39 

15-9-1 

40 

15-4-J 

41 

35-4-^J 

42 

15-15-J 

43 

15-2-K 

44 

35-2-K 

•J  To  obtain  an  approximate  measure  of  the  evaporative  performance  of  the  boiler,  when 
using  West  Virginia  or  Pittsburgh  coal,  multiply  column  44  by  1 . 25. 


METHOD  OF  TESTING  AND  DATA. 


89 


TABLE  VII. 

BOILER  PERFORMANCE— Continued. 


Equivalent  Evaporation  from  and  at  212°  F. 

1 

Labora- 
tory 
Symbol. 

Water 
Evaporater 

Hour. 

Per 

Hour. 

Per 

Square 
Foot  of 
Heating 
Surface 

Per 
Square 
Foot  of 
Grate 
Surface 

Per 

Pound 
of  Dry 
Coal.* 

Per 

Pound 
of  Com- 
bustible 

Boiler 
Horse- 
power 
(34.5 
Evapo- 
rative 

JP 

s 

3 

per  Hour 

per  Hour 

units  = 
1B.H.P.) 

S? 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

1 

2 

46 

47 

48 

49 

50 

51 

52 

1 

15-16-V 

5,617.8 

6,762 

5.57 

392 

8.31 

9.24 

196 

2 

25-1  -V 

7,368.9 

8,864 

7.30 

514 

7.95 

8.84 

257 

3 

35-1-V 

8,528.2 

10,286 

8.47 

596 

7.54 

8.38 

298 

4 

55-1-V 

9,709.2 

11,650 

9.57 

673 

6.98 

7.76 

337 

5 

15-1-A 

5,525.1 

6,660 

5.48 

386 

7.83 

8.70 

193 

6 

25-1-A 

6,092.8 

7,318 

6.03 

424 

8.05 

8.95 

212 

7 

35-1-A 

8,122.5 

9,751 

8.03 

566 

7.74 

8.61 

283 

8 

45-1-A 

8,669.0 

10,395 

8.56 

603 

7.96 

8.83 

301 

9 

55-1-A 

8,941.3 

10,690 

8.80 

619 

7.17 

7.95 

310 

10 

15-2-A 

7,280.2 

8,745 

7.20 

507 

7.95 

8.84 

253 

11 

25-2-A 

9,635.3 

11,555 

9.51 

669 

7.18 

7.98 

335 

12 

35-2-A 

11,441.5 

13,733 

11.31 

796 

6.94 

7.72 

398 

13 

45-2-A 

12,471.6 

14,926 

12.29 

865 

6.09 

6.77 

433 

14 

55-2-A 

14,039.5 

16,773 

13.81 

973 

6.34 

7.04 

486 

15 

25-3-A 

12,931.1 

15,515 

12.77 

899 

6.76 

7.51 

450 

16 

35-3-A 

14,937.4 

17,878 

14.73 

1,037 

5.71 

6.36 

518 

17 

15-9-  A 

11,408.8 

13,670 

11.25 

792 

6.81 

7.57 

396 

18 

35-2-B 

8,666.3 

10,404 

8.57 

604 

6.75 

7.50 

302 

19 

35-2-C 

13,004.2 

15,709 

12.93 

911 

5.86 

6.52 

456 

20 

35-2-E 

8,565.6 

10,324 

8.51 

598 

7.54 

8.38 

299 

21 

35-2-F 

8,111.1 

9,785 

8.06 

567 

7.61 

8.45 

284 

22 

15-1-G 

6,231.9 

7,476 

6.16 

433 

8.37 

9.31 

217 

23 

35-1-G 

9,375.1 

11,226 

9.24 

650 

7.41 

8.24 

325 

24 

35-1&-G 

9,438.8 

11,312 

9.31 

655 

7.72 

8.58 

328 

25 

55-1-G 

10,380.4 

12,425 

10.23 

720 

6.59 

7.33 

360 

26 

35-2-G 

12,317.3 

14,725 

12.12 

853 

6.35 

7.06 

427 

27 

35-3-G 

11,597.2 

13,866 

11.42 

804 

6.87 

7.63 

402 

28 

15-9-G 

11,577.1 

13,869 

11.42 

804 

6.74 

7.49 

402 

29 

15-1-H 

6,074.5 

7,248 

5.97 

420 

9.15 

10.17 

210 

30 

35-1-H 

9,271.2 

11,090 

9.13 

643 

7.12 

7.92 

321 

31 

55-1-H 

10,256.6 

12,302 

10.13 

713 

7.68 

8.54 

356 

32 

35-2-H 

12,366.6 

14,769 

12.16 

856 

6.95 

7.73 

428 

33 

35-26-H 

9,685.9 

11,633 

9.58 

674 

7.18 

7.97 

337 

34 

35-3-H 

11,692.9 

13,993 

11.52 

811 

6.59 

7.32 

406 

35 

15-9-H 

11,457.8 

13,752 

11.32 

796 

6.47 

7.18 

398 

36 

15-1-1 

6,135.2 

37 

35-1-1 

9,453.2 

38 

55-1-1 

11,254.5 

39 

15-9-1 

10,857.3 

40 

15-4-J 

6,556.7 

- 

41 

35-4-J 

10,215.6 

42 

15-15^1 

11,608.7 

43 

15-2-K 

6,710.4 

44 

35-2-K 

10,311.3 

*  To  obtain  an  approximate  measure  of  the  evaporative  performance  of  the  boiler,  when 
using  West  Virginia  or  Pittsburgh  coal,  multiply  column  50  by  1.25. 


90 


LOCOMOTIVE  PERFORMANCE. 


TABLE  VIII. 

ENGINE  PERFORMANCE. 

EVENTS  OF  STROKE  BY  INDICATOR. 


Admission  Per  Cent  of  Stroke. 

Cut-off  Per  Cent  of  Stroke. 

Labora- 
tory 

Right  Side 

Left  Side. 

Right  Side. 

Left  Side. 

Symbol. 

Aver- 

Aver- 

1 

age. 

age. 

1 

H.E 

C.E 

H.E 

C.E. 

H.E. 

C.E. 

H.E. 

C.E. 

1 

2 

53 

54 

55 

56 

57 

58 

59 

60 

61 

62 

1 

15-U-V 

3.05 

6.10 

4.60 

6.60 

5.09 

24.5 

24.8 

25.  OC 

26.  OC 

25.08 

2 

25-1-V 

3.05 

6.10 

4.60 

6.60 

5.09 

24.5 

24.8 

25.  OC 

26.00 

25.08 

3 

35-1-V 

3.05 

6.10 

4.60 

6.60 

5.09 

24.5 

24.8 

25.  OC 

26.00 

25.08 

4 

55-1-V 

Car 

ds  un 

satis! 

actory 

26.04 

25.1 

26.09 

23.95 

25.31 

5 

15-1-A 

2.25 

4.25 

3.50 

3.00 

3.25 

23.5 

25.2 

25.75 

24.25 

24.68 

6 

25-1-A 

2.25 

4.25 

3.50 

3.00 

3.25 

23.50 

25.2 

25.75 

24.25 

24.68 

7 

35-1-A 

2.25 

4.  '25 

3.50 

3.00 

3.25 

23.50 

25.25 

25.75 

24.25 

24.68 

8 

45-1-A 

1.79 

2.64 

1.79 

2.39 

2.15 

21.36 

23.04 

22.97 

22.36 

22.43 

9 

55-1-A 

Car 

Is  un 

atisf 

actory 

23.16 

23.54 

24.98 

22.53 

22.61 

10 

15-2-A 

1.10 

1.70 

1.40 

1.80 

1.50 

39.10 

36.30 

38.80 

37.10 

37.80 

11 

25-2-A 

1.09 

1.86 

1.28 

1.91 

1.53 

33.26 

34.6 

34.92 

34.69 

34.37 

12 

35-2-A 

1.00 

2.50 

2.00 

1.30 

1.70 

32.75 

33.00 

35.25 

33.75 

33.69 

13 

45-2-A 

1.39 

2.40 

1.11 

2.10 

1.75 

32.40 

33.00 

33.80 

33.10 

33.07 

14 

55-2-A 

Car 

s  un 

atisf 

qtory 

35.30 

34.70 

36.60 

36.00 

35.40 

15 

25-3-A 

1.20 

1.90 

1.00 

1.20 

1.32 

44.40 

43.70 

44.80 

44.00 

44.22 

16 

35-3-A 

1.81 

1.69 

0.46 

1.08 

1.51 

43.71 

44.97 

43.98 

42.63 

43.82 

17 

15-9-A 

0.00 

0.00 

0.00 

0.00 

0.00 

80.16 

79.88 

81.30 

79.93 

80.32 

18 

35-2-B 

1.58 

1.77 

1.55 

1.66 

1.64 

29.30 

31.19 

35.13 

30.75 

31.59 

19 

35-2-C 

1.28 

.06 

1.21 

1.75 

1.57 

29.06 

31.23 

35.55 

31.70 

31.88 

20 

35-2-E 

1.61 

.08 

1.67 

1.79 

1.79 

29.01 

30.73 

29.03 

27.13 

28.97 

21 

35-2-F 

1.83 

2.21 

1.83 

1.83 

1.92 

28.20 

30.23 

25.33 

28.14 

27.97 

22 

15-1-G 

Car 

s  un 

atisf 

ctory 

25.69 

26.06 

26.15 

25.32 

25.80 

23 

35-1-G 

Car 

s  un 

atisf 

ctory 

26.89 

25.31 

27.46 

25.72 

26.34 

24 

35-1  6-G 

4.42 

6.47 

3.72 

4.95 

4.89 

25.94 

24.79 

26.84 

24.53 

25.52 

25 

55-1-G 

6.99 

6.51 

4.95 

5.09 

5.89 

25.58 

24.62 

25.36 

23.16 

24.68 

26 

35-2-G 

3.18 

4.12 

3.20 

3.83 

3.58 

35.29 

35.36 

33.77 

34.30 

34.68 

27 

35-3-G 

2.25 

2.56 

2.24 

2.18 

2.31 

45.39 

44.18 

45.89 

45.04 

45.12 

28 

15-9-G 

.95 

1.04 

1.10 

1.12 

1.05 

81.07 

79.83 

80.91 

79.69 

80.38 

29 

15-1-H 

2.35 

3.77 

2.64 

3.19 

2.99 

26.93 

25.90 

26.64 

24.23 

25.92 

30 

35-1-H 

3.24 

5.17 

3.31 

3.74 

3.86 

24.52 

24.80 

27.60 

24.21 

25.28 

31 

55-1-H 

3.21 

3.29 

2.84 

3.02 

3.09 

25.33 

24.58 

25.82 

24.10 

24.96 

32 

35-2-H 

Car 

s  un 

atisf 

ctory 

35.00 

36.42 

37.35 

36.23 

36.25 

33 

35-26-H 

2.77 

2.78 

2.47 

2.22 

2.56 

35.94 

34.45 

37.09 

35.81 

35.83 

34 

35-3-H 

0.32 

2.00 

1.07 

1.77 

1.54 

42.51 

42.53 

45.50 

47.25 

44.45 

35 

15-9-H 

Car 

s  un 

atisf 

ctory 

83.92 

82.87 

83.90 

87.67 

83  35 

36 

15-1-1 

2.20 

3.61 

1.35 

3.35 

2.63 

23.72 

26.34 

24.05 

25.85 

24.99 

37 

35-1-1 

2.50 

4.58 

1.44 

3.29 

2.95 

20.85 

22.61 

19.38 

21.11 

20.99 

38 

55-1-1 

3.16 

3.65 

2.00 

2.93 

2.94 

17.33 

22.10 

18.37 

19.76 

19.39 

39 

15-9-1 

0.00 

0.00 

0.00 

0.00 

0.00 

82.34 

81.77 

83.03 

82.97 

82.53 

40 

15-4-J 

1.27 

1.71 

1.41 

1.65 

1.51 

26.70 

24.03 

27.63 

23.49 

25.46 

41 

35-4-J 

1.39 

1.58 

0.63 

1.51 

1.53 

23.90 

21.92 

25.06 

21.96 

23.21 

42 

15-15-J 

0.00 

0.00 

0.00 

0.00 

0.00 

72.26 

68.31 

70.65 

67.85 

69.76 

43 

15-2-K 

2.10 

2.68 

4.70 

4.70 

3.55 

29.30 

27.51 

29.61 

27.11 

28.38 

44 

35-2-K 

1.99 

2.75 

4.14 

4.33 

3.30 

28.30 

28.22 

30.86 

26.75 

28.53 

METHOD  OF   TESTING  AND  DATA. 


91 


TABLE  IX. 

ENGINE   PERFORMANCE— Continued. 
EVENTS  OF  STROKE  BY  INDICATOR. 


Release  Per  Cent  of  Stroke. 

Compression  Per  Cent  of  Stroke. 

Labora- 
tory 

Right  Side. 

Left  Side. 

Right  Side. 

Left  Side. 

Symbol. 

Aver- 

Aver- 

1 

i 

H.E. 

C.E. 

H.E. 

C.E. 

age. 

H.E. 

C.E. 

H.E. 

C.E. 

age. 

£ 

1 

2 

63 

64 

65 

66 

67 

68 

69 

70 

71 

72 

l 

15-1  &-V 

65.50 

70.00 

66.00 

69.10 

67.65 

38.00 

43.50 

42.00 

45.00 

42.125 

2 

25-1-V 

85.50 

70.00 

66.00 

69.10 

67.65 

38.00 

43.50 

42.00 

45.00 

42.125 

3 

35-1-V 

65.50 

70.00 

66.00 

69.10 

67.65 

38.00 

43.50 

42.00 

45.00 

42.125 

4 

55-1-V 

72.90 

68.27 

73.31 

69.35 

70.96 

21.96 

23.53 

22.37 

23.75 

22.90 

5 

15-1-A 

37.80 

72.00 

73.00 

71.50 

71.08 

31.00 

33.00 

35.50 

34.00 

33.37 

6 

25-1-A 

67.80 

72.00 

73.00 

71.50 

71.08 

31.00 

33.00 

35.50 

34.00 

33.37 

7 

35-1-A 

67.80 

72.00 

73.00 

71.50 

71.08 

31.00 

33.00 

35.50 

34.00 

33.37 

8 

45-1-A 

73.07 

73.04 

75.07 

72.18 

73.34 

21.89 

24.11 

20.82 

23.96 

22.69 

9 

55-1-A 

76.16 

74.13 

73.35 

73.12 

74.20 

22.56 

23.79 

21.15 

22.96 

22.62 

10 

15-2-  A 

75.60 

75.10 

76.00 

76.60 

75.80 

23.50 

23.70 

20.30 

19.40 

21.72 

11 

25-2-A 

74.94 

72.61 

76.00 

74.50 

74.51 

28.12 

27.11 

26.31 

28.44 

27.49 

12 

35-2-A 

77.75 

78.50 

78.00 

77.50 

77.94 

27.75 

28.50 

28.75 

29.50 

28.62 

13 

45-2-A 

77.70 

78.10 

79.20 

78.00 

78.25 

22.60 

23.90 

25.60 

25.90 

24.50 

14 

55-2-A 

76.90 

77.50 

77.60 

75.60 

76.90 

27.40 

27.20 

27.40 

27.30 

27.32 

15 

25-3-A 

78.40 

79.30 

80.90 

79.80 

79.60 

15.80 

17.50 

16.00 

17.20 

16.62 

16 

35-3-A 

81.00 

78.75 

82.06 

80.37 

80.54 

23.29 

25.85 

23.62 

25.21 

24.49 

17 

15-9-  A 

93.54 

93.75 

94.10 

93.04 

93.61 

7.82 

6.57 

8.90 

7.54 

7.71 

18 

35-2-B 

77.75 

80.13 

77.30 

81.65 

79.21 

29.38 

30.66 

29.72 

30.22 

29.99 

19 

35-2-C 

77.58 

78.33 

78.06 

78.95 

78.23 

30.78 

30.78 

25.03 

28.20 

28.69 

20 

35-2-E 

78.70 

79.98 

77.35 

79.30 

78.83 

30.10 

31.40 

28.45 

28.95 

29.72 

21 

35-2-F 

77.21 

78.00 

77.69 

78.05 

77.74 

29.93 

29.45 

30.10 

28.45 

29.48 

22 

15-1-G 

83.10 

61.14 

64.32 

63.00 

62.89 

31.67 

28.18 

31.24 

30.29 

30.34 

23 

35-1-G 

63.88 

62.12 

65.90 

63.38 

63.82 

35.15 

33.81 

33.31 

32.03 

33.57 

24 

35-1  6-G 

64.12 

63.09 

85.11 

64.08 

64.10 

33.63 

35.71 

33.38 

34.14 

34.21 

25 

55-1-G 

65.53 

65.73 

35.77 

66.61 

65.91 

34.73 

37.18 

33.91 

35.94 

35.44 

26 

35-2-G 

69.89 

70.28 

72.37 

68.63 

70.29 

26.25 

27.37 

26.90 

25.40 

26.'48 

27 

35-3-G 

76.00 

75.61 

76.89 

74.93 

75.86 

26.04 

23.57 

24.57 

22.93 

24.28 

28 

15-9-G 

92.39 

92.77 

92.30 

91.21 

92.17 

6.84 

5.45 

7.49 

6.39 

6.54 

29 

15-1-H 

59.16 

59.00 

60.04 

57.74 

58.98 

23.67 

24.66 

24.04 

23.25 

23.90 

30 

35-1-H 

60.33 

57.64 

61.84 

58.18 

59.50 

27,99 

27.86 

28.70 

26.88 

27.86 

31 

55-1-H 

62.08 

59.67 

58.95 

59.35 

60.01 

23.44 

21.37 

20.43 

21.65 

21.72 

32 

35-2-H 

66.29 

67.78 

69.10 

68.00 

67.79 

25.29 

25.80 

24.35 

24.73 

25.04 

33 

35-2&-H 

65.42 

65.27 

68.16 

65.53 

66.09 

24.87 

23.70 

23.78 

22.97 

23.83 

34 

35-3-H 

71.41 

71.65 

73.42 

71.90 

72.10 

21.34 

21.20 

16.44 

19.40 

19.60 

35 

15-9-H 

92.46 

91.47 

92.69 

91.54 

92.04 

6.86 

6.28 

6.65 

6.40 

6.55 

36 

15-1-1 

47.02 

50.82 

48.61 

51.22 

49.42 

15.74 

19.82 

14.60 

19.14 

17.325 

37 

35-1-1 

49.95 

53.05 

49.79 

52.28 

51.27 

16.64 

19.94 

15.00 

18.86 

17.61 

38 

55-1-1 

53.80 

55.33 

53.50 

50.50 

53.28 

19.46 

19.40 

17.87 

19.55 

19.07 

39 

15-9-1 

89.84 

89.08 

90.50 

89.92 

89.84 

9.66 

9.03 

8.76 

8.95 

9.10 

40 

15-4-J 

71.53 

68.74 

70.78 

67.48 

69.63 

33.35 

31.46 

34.48 

31.95 

32.81 

41     35-4^1 

71.35 

68.21 

70.50 

69.56 

69.90 

34.03 

31.10 

32.68 

30.99 

32.20 

42 

15-15-J 

91.62 

89.25 

90.65 

89.53 

90.26 

9.41 

8.64 

11.01 

9.80 

9.71 

43 

15-2-K 

70.76 

68.70 

67.15 

64.86 

67.87 

31.86 

28.85 

35.58 

32.66 

32.24 

44 

35-2-K 

72.47 

71.30 

70.08 

68.41 

70.57 

32.22 

32.03 

34.47 

31.64 

32.59 

92 


LOCOMOTIVE  PERFORMANCE. 


TABLE  X. 

ENGINE    PERFORMANCE— Continued. 
PRESSURES  ABOVE  ATMOSPHERE  BY  INDICATOR. 


Initial  Pressure, 

Pressure  at  Cut-off, 

Pounds  per  Square  Inch. 

Pounds  per  Square  Inch. 

Labora- 
tory 

Right  Side. 

Left  Side. 

Right  Side. 

Left  Side. 

Symbol. 

Aver- 

Aver- 

j 

age. 

« 

age. 

1 

H.E. 

C.E. 

H.E. 

C.E. 

H.E. 

C.E. 

H.E. 

C.E. 

fc 

1 

2 

73 

74 

75 

76 

77 

78 

79 

80 

81 

82 

1 

15-1&-V 

123.10 

126.00 

126.00 

128.65 

125.94 

92.11 

93.68 

103.10 

93.41 

95.57 

2 

25-1-V 

127.90 

132.80 

127.20 

135.00 

130.72 

83.10 

85.40 

88.60 

86.90 

86.00 

3 

35-1-V 

111.78 

115.00 

116.70 

117.30 

115.20 

69.80 

78.14 

75.64 

78.80 

75.59 

4 

55-1-V 

118.17 

123.45 

119.12 

118.09 

119.71 

57.12 

67.64 

67.25 

65.95 

61.99 

6 

15-1-A 

118.20 

120.54 

122.88 

122.60 

121.06 

89.11 

91.75 

91.29 

91.81 

90.99 

6 

25-1-A 

101.48 

100.58 

104.42 

105.58 

103.02 

67.04 

68.88 

70.25 

72.46 

69.66 

7 

35-1-A 

121.80 

120.60 

128.10 

130.00 

125.13 

67.33 

71.20 

70.80 

73.10 

70.61 

8 

45-1-A 

111.40 

111.10 

118.00 

117.50 

114.50 

64.70 

70.70 

64.60 

71.60 

67.90 

9 

55-1-A 

116.93 

120.82 

119.20 

119.64 

119.15 

57.43 

63.75 

54.30 

63.86 

59.83 

10 

15-2  A 

115.30 

122.30 

121.60 

123.60 

120.70 

85.20 

90.90 

84.90 

90.80 

87.90 

11 

25-2-A 

118.40 

117.40 

121.50 

122.80 

120.02 

79.60 

81.50 

83.20 

84.20 

82.12 

12 

35-2-A 

109.38 

119.90 

114.94 

118.17 

115.60 

68.65 

78.00 

72.66 

74.19 

73.37 

13 

45-2-A 

111.10 

116.90 

118.60 

117.30 

115.97 

60.10 

68.20 

60.10 

67.20 

63.90 

14 

55-2-A 

118.00 

118.30 

118.10 

117.40 

117.95 

51.60 

59.30 

52.70 

56.40 

55.07 

15 

25-3-A 

113.30 

119.70 

120.80 

120.90 

118.67 

80.00 

85.40 

84.10 

85.60 

83.70 

16 

35-3-A 

110.88 

122.29 

117.04 

115.83 

116.51 

71.08 

75.58 

73.68 

78.66 

74.75 

17 

15-9-A 

74.80 

75.00 

75.13 

75.76 

75.17 

68.03 

68.16 

70.73 

70.33 

69.30 

18 

35-2-B 

91.25 

93.53 

88.19 

93.22 

91.55 

55.75 

58.39 

53.00 

58.47 

56.40 

19 

35-2-C 

134.00 

140.75 

134.46 

140.00 

137.30 

89.67 

92.67 

86.83 

90.75 

89.98 

20 

35-2-E 

87.59 

89.94 

87.44 

88.72 

88.42 

58.82 

59.18 

62.38 

61.72 

60.52 

21 

35-2-F 

86.72 

87.95 

85.67 

88.20 

87.16 

58.78 

59.56 

65.50 

61.00 

61.21 

22 

15-1-G 

119.86 

119.72 

123.30 

124.03 

121.98 

92.94 

96.64 

98.17 

96.75 

96.12 

23 

35-1-G 

106.64 

107.87 

112.56 

112.57 

109.91 

68.44 

73.28 

71.38 

70.50 

70.90 

24 

35-1  6-G 

110.67 

111.06 

116.44 

118.37 

114.14 

71.52 

74.44 

71.53 

75.81 

74.08 

25 

55-1-G 

99.50 

102.75 

113.00 

114.30 

107.38 

60.50 

65.00 

65.54 

68.50 

64.88 

26 

35-2-G 

116.35 

113.09 

119.53 

123.40 

118.09 

69.96 

73.64 

77.06 

77.23 

74.47 

27 

35-3-G 

81.21 

83.00 

83.75 

82.43 

82.60 

48.93 

52.18 

52.00 

51.25 

51.09 

28 

15-9-G 

80.00 

78.37 

78.75 

80.00 

79.28 

70.03 

69.96 

72.66 

72.66 

71.33 

29 

15-1-H 

118.36 

119.78 

123.44 

123.53 

121.28 

89.14 

93.54 

90.62 

93.78 

91.77 

30 

35-1-H 

107.81 

106.53 

114.90 

115.21 

111.11 

66.63 

72.35 

65.33 

69.50 

88.45 

31 

55-1-H 

Cards 

unsati 

sfactor 

V 

56.42 

60.58 

57.27 

59.80 

58.52 

32 

35-2-H 

106.21 

103.87 

108.41 

110.08 

107.14 

60.96 

62.29 

60.75 

60.58 

61.14 

33 

35-26-H 

84.41 

85.47 

88.45 

87.91 

86.56 

47.16 

50.69 

49.31 

47.97 

48.78 

34 

35-3-H 

71.63 

75.09 

75.09 

73.25 

73.76 

45.45 

49.91 

46.04 

45.50 

46.72 

35 

15-9-H 

76.21 

74.42 

75.00 

76.44 

75.52 

64.92 

65.36 

68.50 

68.22 

66.75 

36 

15-1-1 

114.51 

120.04 

118.52 

123.22 

119.07 

88.19 

94.27 

92.96 

93.29 

92.18 

37 

35-1-1 

110.65 

109.76 

115.47 

119.35 

113.81 

74.83 

83.35 

79.12 

82.76 

79.87 

38 

55-1-1 

98.91 

114.91 

111.25 

115.58 

110.16 

69.50 

69.41 

71.91 

73.41 

71.06 

39 

15-9-1 

71.72 

69.72 

69.42 

72.16 

70.76 

63.52 

65.61 

65.31 

64.58 

64.76 

40 

15-4-J 

119.77 

126.15 

123.91 

124.50 

123.58 

93.92 

96.97 

97.28 

99.33 

96.82 

41 

35-4^1 

119.16 

122.08 

127.91 

128.91 

124.52 

80.86 

85.58 

85.86 

87.00 

84.83 

42 

15-15^1 

88.59 

88.18 

88.28 

90.59 

88.91 

78.46 

78.75 

79.09 

82.00 

79.58 

43 

15-2-K 

119.42 

122.97 

122.92 

123.13 

122.11 

91.70 

92.47 

97.83 

96.87 

94.72 

44 

35-2-K 

115.50 

117.19 

113.25 

120.36 

116.57 

71.75 

72.03 

74.78 

78.86 

74.36 

METHOD  OF  TESTING  AND  DATA 


93 


TABLE  XI. 

ENGINE    PERFORMANCE— Continued. 
PRESSURES  ABOVE  ATMOSPHERE  BY  INDICATOR. 


Pressure  at  Release, 

Pressure  at  Beginning  of  Com- 

Pounds per  Square  Inch. 

pression,  Pounds  per  Square  Inch. 

Labora- 
tory 

Right  Side. 

Left  Side. 

Right  Side. 

Left  Side. 

Symbol. 

Aver- 

Aver 

I 

age. 

age. 

I 

H.E. 

C.E. 

H.E. 

C.E. 

H.E. 

C.E. 

H.E. 

C.E. 

fc 

1 

2 

83 

84 

85 

86 

87 

88 

89 

90 

91 

92 

1 

15-lft-V 

32.50 

29.53 

35.42 

30.76 

32.05 

3.47 

2.95 

2.66 

2.15 

2.81 

2 

25-1-V 

28.90 

28.06 

31.50 

27.90 

29.09 

6.33 

3.98 

3.94 

3.46 

4.43 

3 

35-1-V 

23.14 

24.50 

26.14 

23.70 

24.37 

7.78 

8.57 

7.50 

7.57 

7.86 

4 

55-1-V 

15.96 

20.64 

14.62 

18.54 

17.44 

31.21 

30.23 

27.12 

27.04 

28.90 

5 

15-1-A 

29.16 

28.79 

28.02 

27.63 

28.40 

8.05 

8.71 

4.58 

4.38 

6.43 

6 

25-1-A 

20.40 

19.33 

19.67 

20.33 

19.93 

10.40 

9.15 

6.00 

6.96 

8.13 

7 

35-1-A 

20.47 

20.20 

20.30 

20.80 

20.44 

12.25 

11.60 

9.30 

10.50 

10.91 

8 

45-1-A 

14.90 

17.30 

14.60 

17.50 

16.10 

22.60 

23.00 

24.90 

23.10 

23.40 

9 

55-1—  A 

13.52 

15.45 

13.18 

15.32 

14.37 

24.69 

27.73 

27.30 

28.18 

26.98 

10 

15-2-  A 

38.30 

42.80 

38.60 

39.30 

39.70 

4.60 

7.60 

8.60 

9.30 

7.50 

11 

25-2-A 

32.70 

36.70 

33.20 

34.03 

34.16 

6.00 

7.90 

6.80 

6.50 

6.80 

12 

35-2-A 

25.05 

29.00 

29.02 

27.19 

27.57 

9.50 

12.03 

10.90 

11.50 

10.98 

13 

45-2-A 

21.00 

23.70 

21.30 

24.00 

22.50 

17.25 

21.10 

16.10 

18.80 

18.31 

14 

55-2-A 

19.60 

23.00 

19.40 

22.30 

21.07 

17.30 

21.20 

17.70 

20.40 

19.15 

15 

25-3-A 

40.50 

44.40 

41.30 

42.40 

42.15 

13.40 

13.40 

12.30 

11.80 

12.72 

16 

35-3-A 

34.25 

39.95 

35.36 

38.41 

36.99 

13.75 

16.58 

15.12 

15.66 

15.28 

17 

15-9-A 

56.10 

55.73 

58.43 

57.73 

57.00 

1.80 

2.00 

1.77 

1.73 

1.82 

18 

35-2-B 

18.25 

18.53 

19.56 

17.72 

18.51 

9.06 

9.30 

7.81 

9.34 

8.88 

19 

35-2-C 

31  .  17 

34.21 

34.88 

32.89 

33.28 

11.79 

12.83 

10.08 

12.42 

11.78 

20 

35-2-E 

17.68 

18.12 

20.00 

17.28 

18.27 

9.30 

9.09 

9.56 

9.67 

9.40 

21 

35-2-F 

18.06 

18.89 

18.67 

18.47 

18.52 

8.28 

9.17 

7.67 

9.53 

8.66 

22 

15-1-G 

36.44 

42.83 

37.44 

35.69 

38.10 

4.22 

6.94 

5.25 

4.88 

5.32 

23 

35-1-G 

24.85 

27.72 

26.76 

24.86 

25.05 

7.68 

9.25 

9.47 

9.13 

8.88 

24 

35-1  6-G 

25.59 

28.33 

26.59 

24.97 

26.37 

9.53 

8.73 

9.03 

7.87 

8.79 

25 

55-1-G 

19.91 

20.33 

20.64 

19.20 

20.02 

14.33 

12.42 

14.10 

12.20 

13.26 

26 

35-2-G 

32.25 

33.90 

33.20 

34.13 

33.37 

11.14 

11.25 

9.90 

10.86 

10.78 

27 

35-3-G 

25.93 

26.93 

27.61 

26.78 

26.81 

11.82 

11.36 

10.43 

10.18 

10.95 

28 

15-9-G 

59.16 

57.70 

61.00 

60.28 

59.53 

2.50 

2.67 

2.22 

2.00 

2.35 

29 

15-1-H 

39.50 

43.28 

38.31 

36.91 

39.50 

12.78 

11.41 

10.15 

10.20 

11.13 

30 

35-1-H 

24.42 

29.54 

26.37 

25.75 

26.52 

10.69 

12.04 

9.40 

9.75 

10.47 

31 

55-1-H 

19.33 

22.33 

22.09 

20.20 

20.99 

20.92 

27.25 

23.45 

21.10 

23.18 

32 

35-2-H 

29.25 

31.04 

30.00 

28.71 

29.75 

9.21 

9.66 

9.00 

8.54 

9.10 

33 

35-26-H 

22.25 

24.03 

23.53 

22.75 

23.14 

9.34 

9.97 

9.37 

8.34 

9.25 

34 

35-3-H 

23.86 

26.64 

24.86 

26.33 

25.42 

7.90 

8.68 

10.00 

8.42 

8.75 

35 

15-9-H 

57.03 

57.25 

59.41 

59.19 

58.22 

2.03 

2.31 

2.47 

1.50 

2.  OS 

36 

15-1-1 

44.70 

51.54 

45.93 

44.41 

46.64 

19.70 

14.08 

15.48 

13.00 

15.57 

37 

35-1-1 

30.65 

34.71 

31.18 

31.59 

32.03 

21.76 

18.88 

19.47 

16.35 

19.12 

38 

55-1-1 

21.75 

26.16 

22.66 

26.83 

24.35 

20.41 

22.75 

19.50 

19.00 

20.42 

39 

15-9-1 

56.47 

58.66 

58.00 

57.32 

57.61 

2.18 

00.43 

1.50 

1.26 

1.34 

40 

15-4^1 

32.55 

36.10 

33.31 

31.32 

33.32 

2.10 

2.08 

2.73 

2.51 

2.35 

41 

35-4^1 

24.06 

25.69 

26.85 

23.38 

24.99 

8.03 

9.31 

8.05 

7.35 

8.18 

42 

15-15^7 

56.84 

57.28 

57.68 

56.46 

57.07 

2.71 

1.62 

2.25 

1.81 

2.09 

43 

15-2-K 

36.32 

37.82 

39.60 

37.71 

37.86 

3.96 

4.65 

3.80 

3.83 

4.06 

44 

35-2-K 

24.37 

25.53 

29.03 

25.80 

26.18 

10.19 

10.97 

9.22 

9.78 

10.04 

LOCOMOTIVE  PERFORMANCE. 


TABLE  XII. 

ENGINE   PERFORMANCE— Continued. 
PRESSURES  ABOVE  ATMOSPHERE  BY  INDICATOR. 


Least  Back  Pressure, 

Mean  Effective  Pressure, 

Pounds  per  Square  Inch. 

Pounds  per  Square  Inch. 

i 
i 

Labora- 
tory 

Right  Side. 

Left  Side. 

Right  Side. 

Left  Side. 

Symbol. 

Aver- 

Aver- 

1 

age. 

age. 

1 

H.E. 

C.E. 

H.E. 

C.E. 

H.E. 

C.E. 

H.E. 

C.E. 

1 

2 

93 

94 

95 

96 

97 

98 

99 

100 

101 

102 

1 

15-U-V 

2.18 

1.53 

1.22 

0.92 

1.46 

41.04 

41.97 

47.60 

45.12 

43.93 

2 

25-1-V 

2.65 

2.23 

1.88 

1.19 

1.94 

35.35 

36.98 

43.28 

39.31 

38.73 

3 

35-1-V 

3.53 

3.03 

2.90 

2.18 

2.91 

27.27 

28.68 

35.12 

32.29 

30.84 

4 

55-1-V 

3.21 

4.68 

2.12 

3.28 

3.32 

17.29 

20.67 

19.54 

20.19 

19.42 

5 

15-1-A 

1.62 

1.60 

1.06 

0.94 

1.31 

39.95 

42.83 

46.44 

44.76 

43.50 

6 

25-1-A 

1.80 

2.22 

1.60 

1.43 

1.76 

27.05 

30.08 

33.  SC- 

32.32 

30.83 

7 

35-1-A 

3.70 

3.05 

2.50 

2.77 

3.01 

26.01 

28.40 

SI.  08 

30.73 

29.06 

8 

45-1-A 

2.20 

2.90 

2.70 

2.80 

2.70 

20.90 

22.60 

22.30 

23.80 

22.40 

9 

55-1-A 

2.70 

3.39 

2.25 

2.90 

2.81 

16.63 

17.  Gl 

17.69 

18.33 

17.56 

10 

15-2-A 

0.90 

0.70 

1.20 

0.40 

0.80 

60.93 

62.93 

62.96 

64.32 

62.78 

11 

25-2-A 

3.00 

2.90 

2.47 

2.90 

2.82 

49.12 

52.09 

53.98 

53.85 

52.26 

12 

35-2-A 

5.05 

6.40 

5.16 

5.36 

5.49 

39.38 

42.65 

44.44 

42.21 

42.17 

13 

45-2-A 

5.07 

5.90 

5.10 

5.60 

5.47 

30.69 

33.52 

32.94 

34.14 

32.82 

14 

55-2-A 

4.90 

6.75 

5.10 

6.60 

5.84 

25.33 

26.67 

26.55 

27.10 

26.41 

15 

25-3-A 

3.50 

3.90 

3.40 

3.30 

3.52 

61.18 

64.40 

66.34 

66.14 

64.51 

16 

35-3-A 

8.33 

10.08 

7.91 

10.09 

9.10 

47.86 

49.19 

50.73 

51.14 

49.73 

17 

15-9-  A 

1.C3 

1.75 

1.30 

0.64 

1.18 

66.68 

66.39 

68.68 

68.98 

67.68 

18 

35-2-B 

3.08 

3.41 

2.93 

2.88 

3.07 

27.59 

28.89 

31.13 

29.88 

29.37 

19 

35-2-C 

6.79 

7.41 

7.79 

6.75 

7.19 

47.92 

49.85 

55.13 

50.27 

50.79 

20 

35-2-E 

3.24 

3.35 

3.47 

2.89 

3.24 

27.82 

28.64 

31.  1C 

28.63 

29.08 

21 

35-2-F 

2.89 

2.94 

2.46 

3.13 

2.86 

28.33 

29.54 

30.59 

28.83 

29.32 

22 

15-1-G 

0.36 

1.80 

0.80 

0.14 

0.78 

47.48 

48.07 

49.93 

47.69 

48.39 

23 

35-1-G 

2.91 

2.06 

2.15 

1.43 

2.14 

29.71 

29.92 

33.88 

32.23 

31.43 

24 

35-U-G 

3.00 

2.53 

1.56 

1.87 

2.24 

29.75 

31.32 

33.52 

32.69 

31.82 

25 

55-1-G 

2.92 

3.29 

2.95 

2.85 

3.00 

19.63 

21.21 

23.29 

22.72 

21.71 

26 

35-2-G 

3.96 

5.47 

4.00 

4.56 

4.50 

42.89 

43.07 

47.08 

46!  66 

44.92 

27 

35-3-G 

6.61 

5.11 

4.50 

4.46 

5.17 

31.47 

34.54 

37.15 

36.32 

34.87 

28 

15-9-G 

0.69 

1.43 

0.50 

0.12 

0.69 

69.00 

69.00 

70.41 

71.07 

70.02 

29 

15-1-H 

0.70 

2.23 

0.69 

0.48 

1.01 

45.08 

46.11 

46.55 

44.83 

45.64 

30 

35-1-H 

1.23 

3.75 

1.80 

1.37 

2.04 

29.22 

30.93 

33.57 

31.88 

31.40 

31 

55-1-H 

3.04 

3.29 

2.18 

2.10 

2.65 

20.36 

19.92 

23.55 

22.49 

21.58 

32 

35-2-H 

3.21 

5.33 

3.33 

3.33 

3.80 

37.57 

38.17 

40.82 

40.31 

39.22 

:33 

35-2&-H 

2.59 

2.42 

2.34 

2.10 

2.36 

28.17 

29.92 

31.90 

31.20 

30.30 

:34 

35-3-H 

3.31 

4.31 

2.81 

3.17 

3.40 

31.53 

33.07 

35.27 

35.72 

33.90 

35 

15-9-H 

0.79 

1.54 

1.06 

0.46 

0.96 

65.52 

65.32 

67.44 

68.50 

66.70 

36 

15-1-1 

1.28 

0.17 

0.76 

0.61 

0.71 

37.30 

44.92 

42.17 

44.94 

42.33 

37 

35-1-1 

2.82 

1.97 

1.29 

1.14 

1.81 

25.98 

33.33 

30.71 

34.30 

31.08 

38 

55-1-1 

4.00 

3.66 

2.50 

3.16 

3.33 

20.49 

24.15 

24.37 

25.72 

'23.68 

39 

15-9-1 

2.10 

0.03 

1.42 

0.92 

1.09 

59.80 

62.24 

61.76 

63.04 

61.71 

40 

15-4-J 

0.63 

0.68 

1.19 

0.36 

0.72 

50.84 

50.13 

52.78 

49.58 

50.83 

41 

35-4-J 

3.00 

3.47 

3.08 

2.08 

2.91 

34.55 

34.94 

40.11 

37.75 

36.84 

42 

15-15-J 

1.71 

0.75 

0.94 

0.70 

1.03 

73.24 

74.10 

74.95 

76.86 

74.79 

43 

15-2-K 

0.92 

0.57 

1.08 

1.00 

0.89 

52.63 

51.80 

53.09 

50.05 

51.89 

-44 

35-2-K 

3.14 

3.88 

3.25 

2.28 

3.14 

34.17 

33.78 

40.  oe 

38.03 

36.51 

METHOD  OF   TESTING  AND   DATA. 


95 


TABLE  XIII. 

ENGINE  PERFORMANCE— Continued. 
WEIGHT  OF  STEAM  SHOWN  BY  INDICATOR-CARDS. 


Pounds  Steam  at  Cut-off. 

Pounds  Steam  at  Release. 

Labora- 
tory 

Right  Side. 

Left  Side. 

Right  Side. 

Left  Side. 

Symbol. 

1 

Total. 

Total.. 

1 

H.E. 

C.E. 

H.E. 

C.E. 

H.E. 

C.E. 

H.E. 

C.E. 

1 

2 

103 

104 

105 

106 

107 

108 

109 

110 

Ill 

113 

1 

15-1&-V 

.26352 

.25402 

.29059 

.26872 

1.07685 

.26819 

.25583 

.28372 

.26187 

1.06961 

2 

25-1-V 

.24217 

.23532 

.25616 

.25309 

0.98673 

.24776 

.24565 

.26182 

.24518 

1.00041 

3 

35-1-V 

.21107 

.21924 

.22629 

.23399 

0.89059 

.21660 

.22724 

.23372 

.22223 

0.89978 

4 

55-1-V 

.18443 

.20335 

.18946 

.19103 

0.76827 

.11283 

.20507 

.18726 

.19421 

0.77937 

5 

15-1-A 

.24892 

.25295 

.26866 

.25199 

1.02252 

.25725 

.25780 

.26627 

.25177 

1.03309' 

6 

25-1-A 

.  19828 

.20173 

.21841 

.20891 

0.82733 

.20895 

.20489 

.21728 

.21099 

0.84211 

7 

35-1-A 

.19993 

.20723 

.21998 

.21062 

0.83776 

.20969 

.21039 

.22162 

.21423 

0.85593 

8 

45-1-A 

.17548 

.19777 

.18948 

.19392 

0.75665 

.18243 

.19673 

.19062 

.19471 

0.76850 

9 

55-1-A 

.16958 

.18517 

.17613 

.17824 

0.  709  12 

.18418 

.18764 

.17742 

.18355 

0.73279 

10 

15-2-A 

.34479 

.33852 

.34738 

.34153 

1.37223 

.S3426 

.35169 

.34023 

.33524 

1.36142 

LI 

25-2-A 

.28702 

.29871 

.31464 

.30476 

1.20513 

.29843 

.30696 

.3075C 

.29677 

1.20966 

12 

35-2-A 

.25858 

.27234 

.28397 

.27162 

1.08651 

26542 

.28001 

.28875 

.26782 

1.10200 

13 

45-2-A 

.22603 

.25015 

.23811 

.24589 

0.96018 

23531 

.24814 

.24305 

.24827 

0.97477 

L4 

55-2-A 

.21642 

.23419 

.22518 

.23040 

0.90619 

22533 

.24305 

.22760 

.23225 

0.92823 

i5 

25-3-A 

.36433 

.37349 

.38739 

.37369 

1.49890 

35918 

.37890 

.37711 

.36703 

1.48222 

16 

35-3-A 

.32731 

.34660 

.34338 

.34007 

1.35736 

32928 

.34914 

.34288 

.34416 

1.36546 

L7 

15-9-  A 

.53454 

.52264 

.56200 

.53284 

2.15202 

53132 

.51815 

.55392 

.52534 

2.12873 

18 

35-2-B 

.20289 

.20840 

.22277 

.21062 

0.84468 

22118 

.21961 

.22706 

.21967 

0.88752 

19 

35-2-C 

.29154 

.29929 

.32882 

.30377 

1.22342 

30198 

.31095 

.32490 

,30679 

1.24462 

20 

35-2-E 

.20986 

.20832 

.21765 

.20008 

0.83591 

22054 

.21729 

.23056 

.21191 

0.88030 

21 

35-2-F 

.20589 

.20719 

.20484 

.20419 

0.82211 

22042 

.21833 

.22427 

.21748 

0.88050 

22 

15-1-G 

.26699 

.27713 

.28967 

.26941 

1.10320 

27554 

.29416 

.28809 

.26464 

1.12243- 

23 

35-1-G 

.21709 

.21799 

.23313 

.21207 

0.88028 

.21940 

.22444 

.23783 

.21264 

0.89431 

24 

35-U-G 

.21879 

.21743 

.22966 

.21698 

0.88286 

.22404 

.23067 

.23452 

.21528 

0.90451 

25 

55-1-G 

.19028 

.19452 

.20578 

.19230 

0.78288 

.19738 

.19641 

.20383 

.19147 

0.78909 

26 

35-2-G 

.27234 

.28099 

.28904 

.28264 

1.12501 

.27903 

.28393 

.29562 

.27764 

1.13622 

27 

35-3-G 

.25516 

.25782 

.27295 

.25677 

1.04270 

.26112 

.26055 

.27624 

.25613 

1.05404 

28 

15-9-G 

.55337 

.53405 

.57241 

.54601 

2.20584 

.54767 

.52771 

.56316 

.53403 

2.17257 

29 

15-1-H 

.26712 

.26851 

.27492 

.25433 

1.06488 

.27474 

.28710 

.27541 

.25097 

1.08822 

JO 

35-1-H 

.19869 

.21268 

.21850 

.20094 

0.83081 

.20666 

.21909 

.22327 

.20182 

0.85084 

11 

55-1-H 

.17910 

.18410 

.18812 

.17819 

0.72951 

.18491 

19009 

.19235 

.17779 

0.74514 

}2 

35-2-H 

.24364 

.25282 

.26043 

.24477 

10016C 

.25035 

.26006 

.26621 

.24681 

1.02343 

J3 

35-26-H 

.20597 

.20779 

.22197 

.20418 

0.83991 

.21008 

.21504 

.22689 

.20791 

0.85992 

U 

35-3-H 

.22899 

.24185 

.24796 

.24487 

0.96367 

.23484 

.24664 

.24857 

.24418 

0.97423 

J6 

15-9-H 

.53796 

.52304 

.56394 

.53606 

2.16100 

53232 

.51711 

.55336 

.52769 

2.13048 

16 

15-1-1 

.24169 

.27401 

.26128 

.26575 

1.04272 

.24700 

.28755 

.26234 

.25827 

1.05515 

17 

35-1-1 

.19346 

.22260 

.19810 

.20822 

0.82238 

.20145 

.22598 

.20555 

.20868 

0.841C7 

»8 

55-1-1 

.16121 

.18978 

.17755 

.18210 

0.71064 

.17473 

.19599 

.17111 

.18308 

0.72492 

39 

15-9-1 

.51982 

.51815 

.53847 

.51591 

2.09236 

.51459 

.51416 

.53161 

.50688 

2.06720 

10 

15-4^1 

.27682 

.26256 

.29949 

.26118 

1.10005 

.28630 

.29009 

.29032 

.25849 

1.1252ft 

11 

35_4_j 

.22652 

.22238 

.22927 

.22366 

0.90183 

.23650 

.23179 

.25199 

.22170 

0.94199- 

12 

15-15^1 

.54516 

.51025 

.53423 

.52072 

2.11037 

.52687 

.50627 

.53081 

.49947 

2.06341 

13 

15-2-K 

.31595 

.28291 

.29104 

.27764 

1.16754 

.30944 

.28079 

.30300 

.29747 

1.19070 

44 

35-2-K 

.26119 

.23660 

.23306 

.23175 

0.96261 

.26092 

.22987 

.24006 

.23853 

0.96938 

96 


LOCOMO TIVE  PERFORMANCE. 


TABLE  XIV. 

ENGINE  PERFORMANCE— Continued. 
WEIGHT  or  STEAM  AS  SHOWN  BY  INDICATOR- CARDS. 


2 
3 
4 
5 
6 
7 
8 
9 

10 
11 
12 
13 
14 
15 
16 
17 
18 
19 
20 
21 
22 
23 
24 
25 
26 
27 
28 
29 
30 
31 
32 
33 
34 
35 
36 
37 
38 
39 
40 
41 
42 
43 
44 


Pounds  of  Steam  at  Compression. 

Labora- 
tory 

Right  Side. 

Left  Side. 

Symbol. 

Total. 

H.E. 

C.E. 

H.E. 

C.E. 

2 

113 

114 

115 

116 

117 

15-1&-V 

.00911 

.07131 

.07116 

.07116 

.28274 

25-1-V 

.07870 

.  07452 

.07523 

.07504 

.30409 

35-1-V 

.08383 

.09194 

.08910 

.09195 

.35682 

55-1-V 

.10704 

.10986 

.10201 

.10224 

.42115 

15-1-A 

.07287 

.  07444 

.  06854 

.  06388 

.27973 

25-1-A     .08022 

.07587 

.07351 

.07228 

.30182 

35-1-A     .08611 

.08363 

.08501 

.08378 

.33853 

45-1-A     .08761 

.09453 

.09211 

.09352 

.36778 

55-1-A  ,   .  09399 

.10440 

.09815 

.10197 

.39851 

15-2-A     .  04931 

.05679 

.05483 

.05266 

.21359 

25-2-A     .06009 

.  06323 

.06070 

.06109 

.24511 

35-2-A 

.07127 

.  07550 

.07653 

.07768 

.  30098 

45-2-A 

.07733 

.  08941 

.  08373 

.08814 

.33861 

55-2-A 

.08954 

.  09873 

.09269 

.09610 

.37706 

25-3-A 

.  05408 

.05797 

.  05433 

.05368 

.22006 

35-3-A 

.07087 

.08327 

.07682 

.07882 

.30978 

15-9-A 

.02194 

.02112 

.02448 

.02171 

.08925 

35-2-B 

.07276 

.07179 

.06925 

.  07261 

.  20641 

35-2-C 

.08366 

.08216 

.06689 

.07746 

.31016 

35-2-E 

.07510 

.07280 

.07217 

.07152 

.29158 

35-2-F 

.07232 

.07006 

.07036 

.07086 

.28360 

15-1-G 

.06049 

.06250 

.06426 

.  05946 

.24671 

35-1-G 

.07763 

.  07953 

.08161 

.  07535 

.31412 

35-U-G 

.  08090 

.08128 

.  08036 

.07518 

.31772 

55-1-G 

.09815 

.09605 

.09739 

.09210 

.38369 

35-2-G 

.07106 

.07318 

.07069 

.06775 

.28268 

35-3-G 

.07187 

.  06553 

.06708 

.06095 

.26543 

15-9-G 

.02169 

.02063 

.02346 

.  02078 

.  08656 

15-1-H 

.06931 

.06772 

.06530 

.06155 

.26388 

35-1-H 

.07340 

.07636 

.07280 

.06776 

.  29032 

55-l^H 

.08827 

.09637 

.08798 

.08295 

.35557 

35-2-H 

.06434 

.06613 

.06364 

.06083 

.25494 

35-2&-H 

.06379 

.06292 

.06341 

.05717 

.24729 

35-3-H 

.05333 

.  05479 

.05042 

.  05060 

.20914 

15-9-H 

.02101 

.02116 

.02350 

.02006 

.  08573 

15-1-1 

.06643 

.06442 

.05723 

.06014 

.24721 

35-1-1 

.07150 

.07411 

.06528 

.06614 

.27703 

55-1-1 

.07658 

.07232 

.  07285 

.07327 

.29501 

15-9-1 

.02489 

.02207 

.02393 

.02284 

.09373 

15-4^1 

.  05652 

.  05349 

.06121 

.05500 

.22621 

35-4-J 

.07638 

.07439 

.07551 

.06786 

.29413 

15-15-J 

.02537 

.02332 

.02808 

.02474 

.10151 

15-2-K     .06534 

.  05905 

.  05894 

.  05441 

.23774 

35-2-K     .08145 

.07520 

.07900 

.08028 

.31594 

METHOD  OF  TESTING  A  ND  DATA 


97 


TABLE  XV. 
ENGINE  PERFORMANCE— Continued. 


Indicated  Horse  -power. 

Steam  Used  per 
I.H.P,  per  Hour. 

Dry 

Coal 

Used 

Labora- 
tory 

Right  Side, 

Left  Side. 

Measured 

Measured 

iSfp. 

Symbol 

by 

by 

per 

1 

Total. 

Tank. 

Indicator. 

Hour.* 

1 

H.E. 

C.E. 

H.E. 

C.E. 

fc 

Lbs. 

Lbs. 

Lbs. 

1 

2 

118 

119 

120 

121 

122 

123 

124 

125 

I 

15-H-V 

44.37 

43.98 

51.27 

47.09 

186.71 

29.973 

19.999 

6.903 

2 

25-1-V 

59  .  28 

60.10 

72.31 

63.64 

255.33 

28.780 

19.891 

4.355 

3 

35-1-V 

70.17 

71.51 

90.03 

80.20 

311.91 

27.275 

19.480 

4.359 

4 

55-1-V 

71.72 

83.08 

80.75 

80.84 

316.39 

30.621 

20.423 

5.262 

5 

15-1-A 

44.47 

46.20 

51.51 

48.10 

190.28 

28.929 

19.171 

4.449 

6 

25-1-A 

48.33 

52.08 

60.27 

55.74 

216.42 

28.062 

29.288 

4.188 

7 

35-1  -A 

68.52 

72.52 

81.57 

78.15 

300.76 

26.937 

19.710 

4.184 

8 

45-1  -A 

71.81 

75.24 

76.34 

78.94 

302.33 

28.604 

19.476 

4.329 

9 

55-1-A 

70.15 

71.98 

74.34 

74.64 

291.11 

30.645 

21  .  069 

5.119 

10 

15-2-A 

64.81 

64  86 

66.72 

66  04 

262.43 

27  .  661 

20.233 

4.187 

11 

25  -2  -A 

86.47 

88.86 

94.67 

91  51 

361.51 

26.595 

20.432 

4.449 

12 

35-2-A 

103.24 

108.35 

116.06 

L06.82 

434.47 

26.286 

21.021 

4.543 

13 

45-2-A 

104.20 

110.28 

111.41 

111.89 

437.78 

28.445 

21.457 

5.600 

14 

55-2-A 

106.93 

109.10 

111.66 

110.44 

438.13 

31.997 

23.094 

6.031 

15 

25-3-A 

108.97 

111.14 

117.71 

113.71 

451.53 

28.593 

21  .  657 

5.081 

16 

35-3-A 

121.35 

120.86 

128.15 

125.17 

495.53 

30.103 

23.492 

6.323 

17 

15-9-  A 

72.90 

70.33 

74.80 

72.79 

290.82 

39.162 

33.343 

6.896 

18 

35-2-B 

71.71 

72.76 

80.61 

74.97 

300.05 

28.821 

22.646 

5.130 

19 

35-2-C 

125.32 

126.32 

143.62 

126.90 

522.16 

24.861 

20.354' 

5.120 

20 

35-2-E 

74.52 

74.34 

83.15 

74.02 

306.03 

27.922 

22.410 

4.465 

21 

35-2-F 

73.12 

73.88 

78.65 

71.82 

297.47 

27.184 

22.523 

4.324 

22 

15-1-G 

53.09 

52.09 

55.62 

51.48 

212.28 

29.263 

20.062 

4.205 

23 

35-1-G 

78.03 

75.14 

88.64 

81.71 

324.52 

28.827 

20.420 

4.664 

24 

35-H-G 

78.08 

79.66 

87.64 

82.82 

328.21 

28.696 

20.408 

4.463 

25 

55-1-G 

81.92 

85.78 

96.83 

91.53 

356.06 

29.096 

20.665 

5.293 

26 

35-2-G 

110.77 

107.79 

121.13 

116.33 

456.02 

26.967 

21.023 

5.084 

27 

35-3-G 

82.53 

87.78 

97.06 

91.95 

359.31 

32.220 

25.030 

5.615 

28 

15-9-G 

75.08 

72.75 

76.32 

75.28 

299.43 

38.593 

32.966 

6.871 

29 

15-1-H 

50.65 

50.20 

52.11 

48.62 

201.58 

30.032 

19.980 

3.926 

30 

35-1-H 

76.59 

78.56 

87.65 

80.66 

323.46 

28.602 

19.753 

4.814 

31 

55-1-H 

82.65 

78.36 

95.23 

88.13 

344.37 

29.725 

19.972 

4.651 

32 

35-2-H 

100.14 

98.58 

108.39 

103.71 

410.82 

30.058 

21.683 

5.173 

33 

35-26-H 

74.46 

76.63 

84.00 

79.60 

314.69 

30.719 

22.378 

5.149 

34 

35-3-H 

84.42 

85.81 

94.07 

92.31 

356.61 

32.735 

24.982 

5.956 

35 

15-9-H 

72.42 

69.97 

74.26 

73.09 

289.74 

39.476 

33.924 

7.320 

36 

15-1-1 

41.64 

48.60 

46.90 

48.44 

185.59 

32.943 

21.140 

37 

35-1-1 

68.39 

85.04 

80.55 

87.17 

321.15 

29.366 

21.317 

38 

55-1-1 

84.22 

96.21 

99.81 

102.08 

382.34 

29.383 

19.603 

39 

15-9-1 

65.42 

65.98 

67.32 

66.57 

265.30 

40.865 

35.393 

40 

15-4^1 

58.29 

55.70 

60.29 

54.88 

229.16 

28.520 

19.563 

41 

35-4-J 

90.86 

89.02 

105.06 

95.82 

380.76 

26.772 

19.458 

42 

15-15^1 

79.53 

77.91 

81.05 

80.51 

319.02 

35.130 

29.040 

43 

15-2-K 

0.01 

54.81 

59.71 

56.94 

231.47 

28.810 

20.310 

44 

35-2-K 

84.21 

81.61 

99.50 

91.54 

356.87 

27.820 

20.580 

*  To  obtain  an  aoproximate  measure  of  the  performance  of  the  locomotive    when  using 
West  Virginia  or  Pittsburgh  coal,  multiply  column  125  by  0.8. 


LOCOMOTIVE  PERFORMANCE. 


TABLE  XVI. 

ENGINE  PERFORMANCE—  (Continued]. 
RESULTS  FROM  INDICATOR- CARDS. 


Labora- 

Weight 
Steam 
per 
Revo- 

Weight 
Mixture 

in  Cyl- 
inder 

Per  Cent 
of  Mix- 
ture 
Present 

Per  Cent 
of  Mix- 
ture 
Present 

Reevap- 
oration 
per 

Conden- 
sation 
per 

Reevap- 
oration 

I  H  P 

Conden- 
sation 

I  if  Tp 

tory 

lution 

per 

Revo- 

Revo- 

j 

Symbol. 

by 
Tank. 

Revo- 
lution. 

as 
Steam 
at 

as 
Steam 
at 

lution. 

lution. 

per 
Hour. 

Hour. 

I 

Cut-off. 

Release. 

1 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

Lbs. 

1 

2 

126 

127 

128 

129 

130 

131 

132 

133 

1 

15-1&-V 

1.19011 

1.47285 

73.11 

72.62 

.00724 

.18267 

2 

25-1-V 

1.00752 

1.31161 

75.23 

76.27 

0.01367 

0.39060 

3 

35-1-V 

0.76024 

1.11706 

79.73 

80.55 

.00919 

0.32970 

4 

55-1-V 

0.53705 

0.95820 

80.18 

81.34 

.01110 

0.63293 

5 

15-1-A 

1.13690 

1.41663 

72.18 

72.22 

.01057 

0.39944 

6 

25-1-A 

0.78156 

1  .  08338 

76.37 

77.73 

.01478 

0.53073 

7 

35-1-A 

0.70709 

1.04562 

80.12 

81.86 

.01817 

0.70708 

8 

45-1-A 

0.57873 

0.94651 

79.94 

81.18 

.01185 

0.58587 

9 

55-1-A 

0.48625 

0.88476 

80.15 

82.82 

.02367 

1.49286 

10 

15-2-A 

1.56924 

1.78283 

76.97 

76.36 

.01081 

.  19032 

11 

25-2-A 

1.25553 

1.50064 

80.30 

80.69 

.00453 

0.09615 

12 

35-2-A 

1.00165 

1.30263 

83.41 

84.60 

.01549 

0.40628 

13 

45-2-A 

0.84323 

1.18184 

81.24 

82.48 

.01459 

0.49207 

14 

55-2-A 

0.76357 

1.14063 

79.44 

81.37 

.02204 

0.92330 

15 

25-3-A 

1.66629 

1  .  88635 

79.46 

78.58 

.01668 

.26461 

16 

35-3-A 

1.35278 

1.66256 

81.64 

82.13 

.00810 

0.18023 

17 

15-9-A 

2.39542 

2.48467 

86.61 

85.67 

.02329 

.38076 

18 

35-2-B 

0.76518 

1.05159 

80.32 

84.40 

.  04284 

1.61392 

19 

35-2-C 

1.14142 

1.45159 

84.28 

85.74 

.02120 

0.46180 

20 

35-2-E 

0.73353 

1.02511 

81.55 

85.87 

.04439 

1.68960 

21 

35-2-F 

0.72044 

1  .  004C4 

81.88 

87.70 

.05839 

2.20343 

22 

15-1-G 

1.27736 

1.524C7 

72.38 

73.65 

.01923 

0.44054 

23 

35-1-G 

0.81905 

1.13317 

77.68 

78.92 

.01403 

0.49379 

24 

35-1  6-G 

0.82510 

1.14282 

77.25 

79.15 

.02165 

0.75295 

25 

55-1-G 

0.57080 

0.95449 

82.02 

82.57 

.00621 

0.31655 

26 

35-2-G 

1.09486 

1.37754 

81.67 

82.48 

.01121 

0.27611 

27 

35-3-G 

1.01506 

1.28049 

81.43 

82.32 

.01134 

0.35995 

28 

15-9-G 

2.44208 

2.52864 

87.23 

85.92 

.03327 

.52578 

29 

15-1-H 

1.23895 

.50283 

70.86 

72.41 

.02334 

0.56587 

30 

35-1-H 

0.81161 

.10193 

75.39 

77.21 

.02003 

0.70587 

31 

55-1-H 

0.57981 

0.93540 

77.99 

79.66 

.01563 

0.80128 

32 

35-2-H 

1.06528 

.32022 

75  .  87 

77.52 

.02177 

0.61425 

33 

35-26-H 

0.84097 

.08826 

77.18 

79.02 

.02001 

0.73092 

34 

35-3-H 

1.00251 

.21165 

79.53 

80.41 

.01056 

0.34481 

35 

15-9-H 

2.37938 

2.46511 

87.66 

86.43 

.03052 

.50635 

36 

15-1-1 

1.25908 

1  .  04869 

82.81 

83.80 

.01243 

0.32532 

37 

35-1-1 

0.82364 

1.10067 

74.71 

76.46 

.01942 

0.69249 

38 

55-1-1 

0.64438 

0.93939 

75.64 

77.16 

.01427 

0.65088 

39 

15-9-1 

2.27697 

2.37070 

88.26 

87.19 

.02516 

.45132 

40 

15-4-J 

1.31060 

1.53681 

71.58 

73.22 

.02516 

0.54740 

41 

35-4^J 

0.89140 

1.18553 

76.07 

79.46 

.04015 

1.20500 

42 

15-15^1 

2.37320 

2.47470 

85.28 

83.38 

.04696 

.69510 

43 

15-2-K 

1.35150 

1.58920 

73.47 

70.49 

.02316 

0.49379 

44 

35-2-K 

0.91551 

1.23150 

78.17 

78.18 

.  00677 

0.02132 

METHOD  OF   TESTING  AND  DATA. 


99 


TABLE  XVII. 

LOCOMOTIVE  PERFORMANCE. 


Machine  Friction  of  Engine 

I.H.P.  per  Square 

in  Terms  of 

Foot  of 

Draw- 

Mechan- 

bar Pull 

Draw- 

ical 

Labora- 

Equiva- 

bar or 

Effi- 

1 

tory 
Symbol. 

lent  to 
Average 
ME.P. 

Average 
M.E.P. 

Draw- 
bar Pull 

I.H.P. 

Dynamo- 
meter 
H.P. 

ciency  of 
Engine. 

Heating 
Surface. 

Grate 
Surface. 

fc 

Lbw. 

Lbs. 

Per  Cent. 

1 

2 

134 

135 

136 

137 

138 

139 

140 

141 

I 

15-U-V 

4,806 

5.29 

579 

22.5 

164.2 

87.9 

.154 

10.8 

2 

25-1-V 

4,236 

5.29 

579 

34.9 

220.4 

86.2 

.210 

14.8 

3 

35-1-V 

3,375 

5.29 

579 

53.5 

258.4 

82.8 

.256 

17.1 

4 

55-1-V 

2,123 

5.29 

579 

86.3 

230.1 

72.7 

.260 

18.3 

5 

15-1-A 

4,759 

5.29 

579 

23.1 

167.2 

87.9 

.157 

11.0 

6 

25-1-A 

3,372 

5.29 

579 

37.1 

179.3 

82.9 

.178 

12.5 

7 

35-1  -A 

3,179 

5.29 

579 

54.8 

246.0 

81.8 

.248 

17.4 

8 

45-1-A 

2,449 

5.29 

579 

71.4 

230.9 

76.4 

.249 

17.5 

9 

55-1-A 

1,921 

5.29 

579 

87.7 

203.4 

69.9 

.239 

16.9 

10 

15-2-  A 

6,867 

4.18 

458 

17.5 

244.9 

93.2 

.226 

15.2 

11 

25-2-A 

5,717 

4.18 

458 

28.9 

332.6 

92.0 

.297 

20.9 

12 

35-2-A 

4,615 

4.18 

458 

43.1 

391.4 

90.1 

.357 

25.2 

13 

45-2-A 

3,590 

4.18 

458 

55.8 

382.0 

87.3 

.359 

25.4 

14 

55-2-A 

2,889 

4.18 

458 

69.5 

368.6 

84.1 

.361 

25.3 

15 

25-3-A 

7,057 

3.57 

391 

25.0 

426.5 

94.5 

.370 

26.1 

16 

35-3-A 

5,441 

3.57 

391 

35.6 

459.9 

92.8 

.407 

28.7 

17 

15-9-A 

7,409 

1.69 

185 

7.3 

283.5 

97.5 

.239 

16.8 

18 

35-2-B 

3,214 

4.18 

458 

42.8 

257.3 

85.7 

.247 

17.4 

19 

35-2-C 

5,558 

4.18 

458 

43.0 

479.2 

91.8 

.430 

30.2 

20 

35-2-E 

3,180 

4.18 

458 

44.1 

261.9 

85.6 

.252 

17.7 

21 

35-2-F 

3,209 

4.18 

458 

42.4 

255.1 

85.7 

.244 

17.2 

22 

15-1-G 

5,283 

5.29 

579 

23.2 

189.1 

89.1 

.174 

12.3 

23 

35-1-G 

3,439 

5.29 

579 

54.6 

269.9 

83.2 

.267 

18.8 

24 

35-1  6-G 

3,482 

5.29 

579 

54.6 

273.6 

83.4 

.270 

18.9 

25 

55-1-G 

2,375 

5.29 

579 

86.8 

269.3 

75.6 

.293 

20.6 

26 

35-2-G 

4,915 

4.18 

458 

42.5 

413.5 

90.7 

.375 

26.4 

27 

35-3-G 

3,814 

3.57 

391 

36.8 

322.5 

89.8 

.296 

20.8 

28 

15-9-G 

7,658 

1.69 

185 

7.2 

292.2 

97.6 

.246 

17.4 

29 

15-1-H 

4,997 

5.29 

579 

23.4 

178.2 

88.4 

.166 

11.7 

30 

35-1-H 

3,436 

5.29 

579 

54.5 

269.0 

83.1 

.266 

18.6 

31 

55-1-H 

2,362 

5.29 

579 

84.4 

260.0 

75.5 

.284 

20.0 

32 

35-2-H 

4,291 

4.18 

458 

43.8 

367.0 

89.3 

.338 

23.8 

33 

35-26-H 

3,315 

4.18 

458 

43.5 

271.2 

86.2 

.259 

18.2 

34 

35-3-H 

3,707 

3.57 

391 

37.6 

319.0 

89.5 

.294 

20.7 

35 

15-9-H 

7,299 

1.69 

185 

7.3 

282.4 

97.5 

.238 

16.8 

36 

15-1-1 

4,632 

5.29 

579 

23.2 

162.4 

87.3 

.153 

10.8 

37 

35-1-1 

3,401 

5.90 

646 

61.0 

260.2 

81.1 

.264 

18.6 

38 

55-1-1 

2,591 

5.90 

646 

92.9 

289.4 

75.6 

.315 

22.2 

39 

15-9-1 

6,752 

1.69 

185 

7.3 

258.0 

97.3 

.219 

15.4 

40 

15-4^J 

5,562 

5.29 

579 

23.8 

205.4 

89.7 

.189 

13.  a 

41 

35-4^1 

4,031 

5.50 

602 

56.8 

324.0 

85.1 

.313 

22.1 

42 

15-15^1 

8,185 

2.00 

219 

8.8 

310.2 

97.2 

.263 

18.5 

43 

15-2-K 

5,678 

4.90 

536 

21.8 

209.7 

90.6 

.191 

13.4 

44 

35-2-K 

3,995 

4.90 

536 

48.0 

308.9 

86.6 

.294 

20  7 

100 


LOCOMOTIVE  PERFORMANCE. 


TABLE  XVIII. 

LOCOMOTIVE  PERFORMANCE— (Continued). 


Steam 
Used 

Dry 
Coal 

B.T.U.  Used  by  Engine. 

Coal 
Used 

D.H.P.  Developed 
per  Square  Foot. 

Labora- 
tory 

D!H!P. 

T)  TT  P 

J 

Symbol. 

Hour. 

j-'.jn.  ST. 
per 
Hour.* 

Per 

Minute. 

Per 
I.H.P. 

per 

Per 
D.H.P. 
per 

Run. 

Heating 
Surface. 

Grate 
Surface. 

s 

Minute. 

Minute. 

55 

Lbs. 

Lbs. 

Lbs. 

1 

2 

143 

143 

144 

145 

146 

147 

148 

149 

1 

15-U-V 

34.08 

4.86 

107,890 

5,778 

6,570 

55.88 

.135 

9.5 

2 

25-1-V 

33.34 

5.08 

141,610 

5,446 

6,425 

49.36 

.181 

12.9 

3 

35-1-V 

32.92 

5.24 

164,275 

5,267 

6,357 

39.32 

.212 

14.9 

4 

55-1-V 

42.11 

6.95 

185,707 

5,869 

8,071 

29.80 

.189 

13.4 

5 

15-1-A 

32.92 

4.69 

106,250 

5,584 

6,354 

56.66 

.138 

9.7 

6 

25-1-A 

33.87 

4.90 

116,805 

5,397 

6,514 

37.78 

.148 

10.4 

7 

35-1-A 

32.93 

5.14 

156,083 

5,189 

6,344 

35.55 

.203 

14.3 

8 

45-1-A 

37.45 

5.95 

166,053 

5,492 

7,191 

28.28 

.190 

13.4 

9 

55-1-A 

43.86 

7.01 

170,938 

5,872 

8,404 

26.22 

.167 

11.8 

10 

15-2-A 

29.64 

4.48 

139,656 

5,322 

5,702 

76.69 

.202 

14.2 

11 

25-2-A 

28.91 

4.77 

184,636 

'5,107 

5,551 

67.82 

.274 

19.3 

12 

35-2-A 

29.18 

5.19 

219,844 

5,060 

5,616 

56.00 

.322 

22.7 

13 

45-2-A 

32.59 

6.06 

238,677 

5,452 

6,248 

53.60 

.315 

22.1 

14 

55-2-A 

38.03 

7.59 

267,981 

6,102 

7,270 

46.47 

.304 

21.3 

15 

25-3-A 

30.27 

5.77 

248,051 

5,493 

5,815 

95.60 

.351 

24.7 

16 

35-3-A 

32.44 

6.79 

285,931 

5,770 

6,217 

91.74 

.379 

26.7 

17 

15-9-  A 

40.17 

7.13 

218,483 

7,512 

7,706 

136.19 

.233 

16.4 

18 

35-2-B 

33.62 

5.36 

166,387 

5,545 

6,466 

44.05 

.213 

14.9 

19 

35-2-C 

27.09 

5.23 

251,132 

4,809 

5,228 

76.02 

.395 

27.8 

20 

35-2-E 

32.63 

5.22 

164,943 

5,389 

6,298 

37.94 

.216 

15.3 

21 

35-2-F 

31.71 

4.97 

156,202 

5,251 

6,125 

37.00 

.210 

14.8 

22 

15-1-G 

32.85 

4.77 

119,319 

5,620 

6,310 

59.26 

.156 

11.0 

23 

35-1-G 

34.66 

5.65 

179,366 

5,527 

6,645 

42.78 

.222 

15.6 

24 

35-U-G 

34.42 

5.63 

180,721 

5,506 

6,605 

41.43 

.225 

15.9 

25 

55-1-G 

38.38 

6.53 

198,585 

5,577 

7,374 

33.52 

.222 

15.6 

26 

35-2-G 

29.74 

5.48 

235,413 

5,162 

5,680 

66.64 

.341 

24.0 

27 

35-3-G 

35.89 

6.40 

221,649 

6,168 

6,873 

57.12 

.266 

18.7 

•28 

15-9-G 

39.55 

7.07 

221,657 

7,403 

6,169 

140.38 

.241 

16.9 

29 

15-1-H 

33.97 

4.87 

115,673 

5,738 

6,491 

52.29 

.147 

10.3 

30 

35-1-H 

34.39 

5.57 

177,190 

5,478 

6,587 

44.10 

.222 

15.6 

31 

55-1-H 

39.37 

5.89 

196,619 

5,709 

7,562 

29.30 

.214 

15.1 

32 

35-2-H 

33.90 

6.20 

236,330 

5,752 

6,439 

59.19 

.302 

21.3 

33 

35-2&-H 

35.64 

5.91 

185,912 

5,907 

6,855 

45.51 

.223 

15.7 

34 

35-3-H 

36.60 

6.57 

223,693 

6,272 

7,012 

58.89 

.261 

18.5 

35 

15-9-H 

40.50 

7.19 

219,289 

7,568 

7,783 

142.46 

.233 

16.4 

36 

15-1-1 

37 

35-1-1 

38 

55-1-1 

39 

15-9-1 

40 

15-4-J 

41 

35-4^1 

42 

15-15-J 

43 

15-2-K 

44 

35-2-K 

*  To  obtain  an  approximate  measure   of  the  performance  of  the  locomotive,  when  using 
West  Virginia  or  Pittsburgh  coal,  multiply  the  values  of  column  143  by  0.8. 


METHOD  OF   TESTING  AND  DATA. 


101 


TABLE  XIX. 

LOCOMOTIVE  PERFORMANCE— (Continued). 

The  values  of   this  table  were   computed   on   the  assumption   of  uniform  fire 
conditions.     The  process  involved  is  developed  in  Chapter  VI. 


Equiva- 
lent 

Coal 
Burned 

Water 

/L  __ 

Equiva- 
lent 

B.T.U. 

Labora- 

Evapo- 
ration 
from 

Coal 
Fired 

per 
Square 
Foot 

T^k) 
Evapo- 

Evapo- 
ration 
from 

Coal 
I.  Si.  P. 

Coal 

D.H!P. 

Taken 
up  by 
Boiler 

j 
I 

tory 
Symbol. 

and  at 
212°  F. 

Hour. 

Hour. 

Grate 
Surface 

Hour. 

rated 
per 
Pound 
of  Coal. 

and  at 
212°  per 
Pound 
of  Coal. 

per 
Hour. 

Hour. 

per 
Pound 
of  Coal. 

fc 

Lbs. 

Lbs. 

Lbs. 

Lbe. 

Lbs. 

Lbs. 

Lbs. 

1 

2 

150 

151 

153 

153 

154 

155 

156 

157 

1 

15-1&-V 

6,762 

798.0 

46.2 

7.04 

8.44 

4.270 

4.86 

8,151.3 

2 

25-1-V 

8,864 

1,113.1 

64.5 

6.62 

7.93 

4.359 

5.05 

7,658.8 

3 

35-1-V 

10,286 

1,349.3 

78.9 

6.32 

7.59 

4.325 

5.22 

7,330.4 

4 

55-1-V 

11,650 

1,590.3 

92.1 

6.10 

7.27 

5.026 

6.91 

7,021.5 

5 

15-1-A 

6,660 

791.6 

.45.8 

6.98 

8.37 

4.160 

4.73 

8,083.7 

6 

25-1-A 

7,318 

876.6 

50.8 

6.95 

8.31 

4.050 

4.89 

8,025.8 

7 

35-1-A 

9,751 

1,261.2 

73.0 

6.44 

7.71 

4.193 

5.13 

7,446.3 

8 

45-1-A 

10,395 

1,367.3 

79.2 

6.34 

7.56 

4.522 

5.92 

7,300.1 

9 

55-1-A 

10,690 

1,416.8 

82.1 

6.31 

7.49 

4.867 

6.97 

7,253.8 

10 

15-2-A 

8,745 

1,093.1 

63.3 

6.66 

7.96 

4.165 

4.46 

7,687.7 

11 

25-2-A 

11,555 

1,590.0 

92.1 

6.06 

7.23 

4.398 

4.78 

6,982.7 

12 

35-2-A 

13,733 

2,028.6 

117.7 

5.64 

6.75 

4.669 

5.18 

6,519.1 

13 

45-2-A 

14,926 

2,301.0 

133.4 

5.42 

6.46 

5.256 

6.02 

6,239.1 

14 

55-2-A 

16,773 

2,802.3 

162.2 

5.01 

6.02 

6.396 

7.78 

5,814.1 

15 

25-3-A 

15,515 

2,444.4 

141.6 

5.29 

6.02 

5.414 

5.73 

6,103.8 

16 

35-3-A 

17,878 

3,099.0 

179.6 

4.82 

5.75 

6.254 

6.74 

5,553.3 

17 

15-9-  A 

13,670 

2,040.9 

118.2 

5.59 

6.67 

7.018 

7.20 

6,441.8 

18 

35-2-B 

10,404 

1,371.5 

79.5 

6.32 

7.56 

4.571 

5.33 

7,300.4 

19 

35-2-C 

15,709 

2,496.0 

144.6 

5.21 

6.27 

4.780 

5.21 

6,055.5 

20 

35-2-E 

10,324 

,355.3 

78.5 

6.32 

7.58 

4.428 

5.17 

7,320.7 

21 

35-2-F 

9,785 

,263.4 

73.2 

6.42 

7.71 

4.247 

4.95 

7,446.3 

22 

15-1-G 

7,476 

900.0 

52.1 

6.93 

8.27 

4.239 

4.76 

7,987.1 

23 

35-1-G 

11,226 

,517.0 

87.9 

6.18 

7.36 

4.674 

5.62 

7,108.3 

24 

35-1  6-G 

11,312 

,532.2 

88.8 

6.16 

7.34 

4.668 

5.60 

7,089.0 

25 

55-1-G 

12,425 

,747.5 

101.2 

5.94 

7.07 

4.908 

6.49 

6,828.2 

26 

35-2-G 

14,725 

2,256.0 

130.7 

5.46 

6.50 

4.947 

5.46 

6,277.7 

27 

35-3-G 

13,866 

2,052.6 

113.1 

5.65 

6.72 

5.712 

6.36 

6,490.2 

28 

15-9-G 

13,869 

2,049.0 

118.8 

5.65 

6.72 

6.843 

7.01 

6,490.2 

29 

15-1-H 

7,248 

866.5 

50.2 

7.01 

8.32 

4.298 

4.86 

8,035.2 

30 

35-1-H 

11,090 

1,490.5 

86.3 

6.22 

7.40 

4.608 

5.54 

7,146.9 

31 

55-1-H 

12,302 

1,675.8 

97.1 

6.12 

7.34 

4.866 

6.45 

7,052.2 

32 

35-2-H 

14,769 

1,959.8 

113.6 

6.31 

7.50 

4.770 

5.34 

7,243.5 

33 

35-26-H 

11,633 

1,593.0 

92.3 

6.08 

7.26 

5.062 

5.87 

7,011.7 

34 

35-3-H 

13,993 

2,080.  6 

120.7 

5.62 

6.69 

5.834 

6.52 

6,461.2 

35 

15-9-H 

13,752 

2,031.5 

117.8 

5.64 

6.72 

7.012 

7.19 

6,490.2 

36 

15-1-1 

37 

35-1-1 

38 

55-1-1 

39 

15-9-1 

40 

15-4-J 

41 

35-4-J 

42 

15-15-J 

43 

15-2-K 

44 

35-2-K 

II.   LOCOMOTIVE  PERFORMANCE, 
A  TYPICAL  EXHIBIT. 


CHAPTER    V. 

LOCOMOTIVE  PERFORMANCE  AS  AFFECTED  BY  CHANGES  IN 
SPEED  AND   CUT-OFF. 

29.  Purpose. — It  is  the  purpose  of  the  present  chapter  to  define 
and  summarize  certain  fundamental  facts  concerning  cylinder  per- 
formance.    It  shows,  by  means  of  data  derived  from  experiments, 
the  effect  of   changes  in  speed   and  cut-off  upon   the    power   and 
efficiency  of  a  locomotive  when  running  under  a  wide-open  throttle. 

30.  The  Tests  which  form  the  basis  for  this  discussion,  twelve  in 
number,  are  those  which,  in  the  tabulated  record  of  Chapter  IV.,  are 
designated  as  Series  A.     They  cover  practically  all  conditions  of  speed 
and  cut-off  at  which  it  is  possible  to  operate  continuously  the  experi- 
mental locomotive  with  a  wide-open  throttle.     Five  tests  were  run 
with  the  reverse  lever  in  the  first  notch,  giving  a  cut-off  of  approxi- 
mately 25  per  cent,  the  speeds  being  15,  25,  35,  45  and  55  miles  per 
hour,  respectively;   five  were  run  with  the  reverse  lever  in  the  sec- 
ond notch,  giving  a  cut-off  of  approximately  35  per  cent,  the  speeds 
being  the  same  as  for  the  shorter  cut-off,  and  two  were  run  with  the 
reverse-lever  in  the  third  notch,  giving  a  cut-off  of  approximately 
45  per  cent.,  the  speeds  being  25  and  35  miles  per  hour,  respectively. 
The  steam  pressure,  the  setting  of  the  valves,  the  fuel  used,  and  the 
fireman  were  the  same  for  all  tests.     Excepting  as  to  speed  and  cut- 
off, which  were  as  specified  above,  the  conditions  affecting  all  tests 
were  as  nearly  as  possible  identical. 

Table  XX.  presents  the  laboratory  symbol  of  the  several  tests 
and  a  summary  of  the  more  important  controlling  conditions. 

102 


CHANGES  IN  SPEED  AND   CUT-OFF. 


103 


TABLE  XX. 
ESSENTIAL  CONDITIONS. 


Speed. 

Cut-off. 

Steam 
Pressure. 

1 

H 
«a 

g 

||] 

JS.S  o 

jD  O 

<D 

Throttle. 

Fuel. 

Fireman. 

o 
ig 

c3 
C 

h 

|| 

Sri 

•8*8* 

mi 

II* 

l! 

.Is 

|i 

-w  o>  o  53 

•stfzu 

|£l 

1 

PH 

PH 

< 

f  Brazil 

] 

15-1-A 

15.00 

80.7 

1 

25 

125.9 

124.6 

Wide  open 

•{  Indiana 

1-  Chas.  Reyer 

[    Block 

J 

25-1-A 

24.07 

129.5 

1 

25 

120.0 

113.4 

" 

" 

" 

35-1-A 

35.49 

191.0 

1 

25 

129.7  127.2 

" 

'  ' 

11 

45-1-A 

46.29 

249.1 

1 

25 

128.8 

124.9 

" 

" 

M 

55-1-A 

56.83 

305.7 

1 

25 

124.9 

121.3 

'  ' 

'  ' 

" 

f   Brazil 

1 

15-  2-  A 

14.33 

77.1 

2 

35 

129.5 

125.1 

Wide  open 

•{  Indiana 

\  Chas.  Reyer 

L    Block 

J 

25-2-A 

23.72 

127.6 

2 

35 

129.3 

124.9 

" 

" 

35-2-A 

35.31 

190.0 

2 

35 

131.6 

120.7 

t  c 

c  c 

" 

45-2-A 

45.74 

246.1 

2 

35 

126.7 

121.1 

c  c 

" 

" 

55-2-A 

56.81 

306.0 

2 

35 

124.0 

118.8 

(  C 

C  I 

'  ' 

f  Brazil 

1 

25-3-A 

24.00 

129.1 

3 

45 

127.2 

123.2 

Wide  open 

•{  Indiana 

}•  Chas.  Reyer 

I   Block 

J 

35-3-A 

34.15 

183.8 

3 

45 

125.3 

122.1 

31.  The  Valves  and  their  Setting. — The  slide-valves  used  in  this 
series  of  tests  had  f"  outside  lap,  -£%"  inside  lap,  and  a  maximum 
travel   of  5.57".     Their  setting  was   that  which,  after  considerable 
experimenting,  had  been  found  to  produce  the  most  efficient  results- 
When  the  cut-off  was  25  per  cent  of  the  stroke,  they  gave  ^y  lead. 
At  full  stroke,  the  lead  was  nil.     (See  A  setting,  Chapter  III.) 

32.  Indicator-cards. — In   Fig.  61    are   presented   average   cards 
f  :om  the  left  side  of  the  locomotive  for  each  test.     These  cards,  when 
studied  in  connection  with  the  results  derived  from  them,  will  serve 
to  disclose  the  effect  upon  the  distribution  of  steam  in  the  cylinder, 
of  changes  in  speed  and  cut-off.     Comparisons  along  vertical  lines 
show  the  effect  of  changes  in  speed  at  constant  cut-off,  along  hori- 
zontal lines,  of  changes  in  cut-off  at  constant  speed. 

Examining  the  cards  along  either  of  the  vertical  lines,  as,  for 
example,  along  that  which  represents  a  cut-off  of  25  per  cent,  it  appears 


104 


LOCOMOTIVE  PERFORMANCE. 


that  as  the  speed  is  increased,  the  size  of  the  card  is  diminished.  At 
very  high  speeds  the  card  is  comparatively  small.  This  change  occurs 
notwithstanding  the  fact  that  there  is  no  change  in  cut-off  or  in  any 
other  event  of  the  stroke.  It  is  due  wholly  to  wiredrawing  past 
the  valves.  While  the  extent  of  port  opening  may  be  unaffected  by 
changes  in  speed,  the  period  of  opening  is  reduced  as  the  speed  is 


45 


I25 

a 


15 


188 


135 


81 


25  35  45 

Cut-off -Notches  and  Per  Cent  of  Stroke 

FIG.  61. 

increased,  from  which  it  necessarily  follows  that  there  is  admitted 
less  steam  per  stroke  as  the  speed  is  increased.  A  further  discussion 
of  this  matter  will  be  found  in  Chapter  XVII.,  which  deals  especially 
with  valve-gears.  It  will  be  sufficient  for  the  present  to  observe  that 
the  size  of  the  card  is  controlled  to  a  limited  extent  only  by  the  cut- 
off. Thus,  by  reference  to  Fig.  61,  it  will  be  found  easy  to  select  cards 
representing  a  cut-off  of  35  per  cent  which  are  actually  smaller  than 
others  representing  a  cut-off  of  25  per  cent. 


CHANGES  IN  SPEED  AND  CUT-OFF.  105 

An  interesting  illustration  of  the  influence  of  speed  upon  the  size  or 
the  card  is  afforded  when  an  attempt  is  made  to  operate  a  locomotive 
with  the  reverse-lever  in  its  extreme  forward  position  at  high  speed. 
Fig.  62  represents  two  cards,  both  taken  with  the  reverse-lever  in  its 
extreme  forward  position.  The  dotted  line  is  the  normal  card  taken 
at  low  speed,  the  full  line  a  card  taken  at  35  miles  an  hour.  It  will 
be  seen  that  the  total  pressure  range  for  the  card  at  speed 'is  divided 
into  three  parts,  more  than  a  third  representing  the  loss  in  passing 


130 
100- 


50  ,  M.E.P.  52.3 


FIG.  62. 

from  boiler  to  cylinder,  a  quarter  from  cylinder  to  exhaust,  and 
approximately  a  third  only  the  mean  effective  pressure.  It  is  evident 
that  speed  as  well  as  cut-off  have  an  important  influence  on  mean 
effective  pressure. 

In  this  connection,  also,  attention  should  be  called  to  the  changed 
form  of  the  card  which  results  from  change  of  speed  (Fig.  61).  At 
low  speeds  the  events  of  the  stroke  are  rather  clearly  marked,  but 
as  the  speed  is  increased  these  become  less  and  less  distinct.  These 
statements  will  be  sufficient  to  show  how  much  more  complicated 
is  the  study  of  locomotive  performance  than  is  that  of  stationary 
engines  designed  to  run  at  fixed  speeds,  for  in  locomotive  service 
the  element  of  speed  appears  as  an  ever-present  influence  affecting 
other  factors;  for  example,  the  mean  effective  pressure,  the  distri- 
bution of  steam,  the  thermodynamic  efficiency,  and  even  the  machine 
friction. 

33.  Events  of  the  Stroke. — In  the  early  work  upon  the  loco- 
motive it  was  assumed  that  a  fixed  location  of  the  reverse-lever 
would  serve  to  maintain  all  events  of  the  stroke  constant.  It  was 
soon  found,  however,  that  the  cut-off,  for  example,  could  not  be 
depended  upon  to  remain  constant  even  though  the  reverse-lever 
was  not  moved,  but  that  a  change  in  the  speed  of  the  locomotive  or 
in  the  lubrication  of  its  valves  was  quite  sufficient  to  materially 
affect  the  time  of  action  of  the  valves.  This  is  to  be  -accounted  for 
by  the  fact  that  the  width  of  port-opening  is  small,  the  force  required 


106 


LOCOMOTIVE  PERFORMANCE. 


to  move  the  valve  is  considerable,  and  the  mechanis  mwhich  drives 
it  is  not  sufficiently  stiff  nor  so  free  from  lost  motion  as  to  impart 
to  the  valve  a  motion  which  is  absolutely  positive.  The  precise 
values  representing  the  several  events  of  the  stroke  for  each  of  the 
twelve  tests  under  consideration,  as  obtained  from  indicator-cards 
taken  under  the  conditions  defined,  are  given  in  Table  XXI.  Cards 
taken  at  high  speeds  do  not  show  clearly  the  point  of  admission,  the 
value  of  which  is  therefore  omitted  from  the  table. 

TABLE  XXI. 
EVENTS    OF   STROKE   AS   DETERMINED   FROM  INDICATOR-CARDS. 

The  values  given  are  the  averages  for  the  four  cylinder-ends. 


Per  Cent 

of  Stroke. 

D     ' 

of  Test. 

Admission. 

Cut-off. 

Release. 

Beginning  of 
Compression. 

15-1-A 

3.25 

24.68 

71.08 

33.37 

25-1-A 

3.25 

24.68 

71.08 

33.37 

35-1-A 

3.25 

24.68 

71.08 

33.37 

45-1  -A 

2.15 

22.43 

73.34 

22.69 

55-1  -A 



22.81 

74.20 

22.62 

15  -2-  A 

1.50 

37.80 

75.80 

21.71 

25-2-A 

1.53 

34.37 

74.51 

27.49 

35-2-A 

1.70 

33.69 

77.94 

28.62 

45-2-A 

1.75 

33.07 

78.25 

24.50 

55-2-A 



35.40 

76.90 

27.32 

25-3  -A 

1.32 

44.22 

79.60 

16.62 

35-3-A 

1.51 

43.82 

80.54 

24.49 

34.  Wiredrawing  between  boiler  and    cylinder  in  a  locomotive 
is  unavoidable,  the  extent  of  its  influence  in  any  given  locomotive 
depending  upon  the, rate  at  which  steam  is  used.     The  areas  of  the 
wide-open    throttle,  steam-pipe,  branch  pipes,  etc.,  for  locomotive 
Schenectady  No.   1  are  shown  graphically  by  Fig.  54,  Chapter  III. 
The  facts  concerning  the  drop  in  the  pressure  of  the  steam  from  the 
boiler  to  the  exhaust-pipe,  with  related  data  of  interest  for  the  twelve 
tests  under  consideration,  are  shown  by  Table  XXII. 

35.  Mean  Effective  Pressure,  as  affected  by  speed  and  cut-off, 
is  shown  diagrammatically  by  Fig.  63.     If  the  values  of  this  figure 
are  compared  along  vertical  lines,  'the  very  striking  effect  resulting 
from  changes  in  speed  may  be  seen.      With  a  given  cut-off  each 


CHANGES  IN  SPEED   AND  CUT-OFF. 


107 


increment  in  speed  reduces  the  amount  of  work  done  per  stroke, 
and  while  values  measuring  such  changes  depend  somewhat  upon 
the  size  of  ports  and  the  characteristics  of  the  valve-gear  employed, 
the  presence  of  such  a  change  is  unavoidable  in  the  action  of  a  loco- 
motive. (Chapter  XVII.) 

TABLE  XXII. 

DROP  IN   STEAM  PRESSURE. 
WIDE-OPEN  THROTTLE.     EXHAUST  TIP  DOUBLE  3"  DIAM. 


Desig- 
nation 
of 
Test. 

15-1-A 
25-1-A 
35-1-A 
45-1-  A 
55-1  A 

Steam 
Ex- 
hausted 
per 
Hour. 
Lbs. 

Maximum  Port- 
opening,  Inches. 

Pressure  of  Steam  in 

Steam. 

Ex- 
haust. 

Boiler. 

Branch 
Pipe. 

124.6 
113.4 
127.2 
124.9 
121.3 

Cylinders 

At 
Cut-off. 

At 
Release  . 

At 
Com- 
pression. 

Least 
Back. 

5,505 

6,073 
8,102 
8,648 
8,921 

.20 
.20 
.20 
.20 
.20 

.92 
.92 
.92 
.92 
.92 

125.9 
120.0 
129.7 

128.8 
124.9 

91.0 
69.7 
70.6 
67.9 

59.8 

28.4 
19.9 
20.4 
16.1 
14.4 

6.4 
8.1 
10.9 
23.4 
26.9 

1.3 

1.8 
3.0 

2.7 
2.8 

15-2-A 
25-2-A 
35-2-A 
45-2-A 
55-2-A 

7,259 
9,614 
11,420 
12,451 
14,019 

.25 
.25 
.25 
.25 
.25 

.97 
.97 
.97 
.97 
.97 

129.5 
129.3 
131.6 
126.7 
124.0 

125.1 
124.9 
120.7 
122.1 

181.8 

87.9 
82.1 
73.4 
63.9 
55.0 

39.7 
34.2 
27.6 
22.5 
21.1 

7.5 
6.8 
11.0 
18.3 
19.1 

0.8 
2.8 
5.5 
5.5 

5.8 

25-3-A 
35-3-A 

12,910 
14,917 

.30 
.30 

1.02 
1.02 

127.2 
125.3 

123.2 
122.1 

83.8 

74.7 

42.1 
37.0 

12.7 
15.3 

3.5 
9.1 

Another  fact  of  interest  in  connection  with  Fig.  63  is  that  the 
values  given  cover  practically  the  entire  range  of  action  under  which 
the  experimental  locomotive  can  be  operated  with  a  wide-open 
throttle.  An  attempt  to  run  a  test  at  15  miles  and  10"  cut-off  resulted 
in  so  high  a  tractive  power  that  the  drivers  slipped,  while  a  test  at 
45  miles  and  10"  cut-off  could  not  be  run  because  of  the  failure  of 
the  boiler  to  supply  steam. 

36.  The  Indicated  Horse-power  for  different  speeds  and  cut-offs 
is  shown  by  Fig.  64.  Here  it  will  be  seen  that  at  constant  cut-off, 
the  power  increases  with  increase  of  speed  up  to  a  certain  point,  after 
which  it  remains  practically  constant.  In  the  case  of  the  locomo- 
tive experimented  upon,  the  maximum  power  was  practically  reached 
at  a  speed  of  35  miles  an  hour.  The  limit,  however,  as  applied  to 


108 


LOCOMOTIVE  PERFORMANCE. 


locomotives  in  general  will  depend  upon  the  proportion  of  the  cylinders, 
the  diameter  of  the  drivers,  and  the  capacity  of  the  boiler,  and  while 
this  point  may  not  always  be  as  clearly  defined  as  it  is  by  the  data 
from  Schenectady  No.  1,  its  presence  will  appear  in  all  locomotives 
which  are  designed  to  run  at  high  speeds  of  rotation. 

It  will  be  seen  that  the  highest  power  reached  was  496  horse. 
Prior  to  the  tests  herein  described,  no  one  knew  what  was  the 
maximum  power  of  a  locomotive  under  constant  operating  con- 


3 
Cut-Off 


Reverse  Lever  Notch 


FIG.  63. — Mean  Effective  Pressure. 

ditions,  though  it  was  not  uncommon  for  locomotives  of  the  size  of 
Schenectady  No.  1  to  be  credited  with  as  high  as  800  horse-power. 
The  facts  presented  by  Fig.  64  and  the  fuller  exhibit  of  Table  XV. 
suggest  that  such  an  estimate  is  too  high,  though  if  a  superior 
grade  of  coal  had  been  used  instead  of  the  light  and  friable  Brazil 
block,  it  is  probable  that  the  maximum  could  have  been  made  to 
approach  600.  It  may  easily  be  shown,  by  an  analysis  based  on  the 
dimensions  of  the  locomotive  and  the  experimental  facts  herein 
presented,  that  for  all  speeds  below  18  miles  an  hour  the  cut-off, 


CHANGES  IN  SPEED   AND   CUT-OFF. 


109 


with  a  fully  open  throttle,  is  limited  by  the  adhesion  of  the  drivers : : 
for  speeds  above  18  miles  the  limit  is  found  in  the  capacity  of  the 
boiler  to  supply  steam.     The  cut-off  which  at  any  given  speed  will 
serve  under  a  fully  open  throttle  to  operate  the  experimental  loco- 
motive at  500  horse-power  is  that  shown  by  the  curve,  Fig.  64. 


3  Reverse  Lever  Notch 

Cut-Off 

FIG.  64. — Indicated  Horse-power. 

It  is  well,  also,  to  review  the  values  of  Fig.  64  with  reference  to  a. 
matter  which  is  always  of  interest  to  locomotive  designers,  namely,, 
that  of  controlling  speed  by  the  reverse-lever  vs.  the  throttle.  The 
reverse-lever  quadrant  of  Schenectady  No.  1  was  notched  at  intervals 
of  {  of  an  inch,  and  the  first  three  notches  forward  from  the  center  gave 
25,  35,  and  45  per  cent  cut-off  respectively.  Fig.  64  discloses  the  fact 
that  at  all  speeds  a  change  of  one  notch  in  the  reverse-lever  position 
makes  a  very  marked  alteration  in  the  power  output,  the  differences 
ranging  from  70  to  146  horse-power.  Between  the  first  and  second 
notches  there  is  an  increase  of  about  50  per  cent  over  the  power 
developed  with  the  lever  in  the  first  notch.  Evidently  no  very  fine 
gradation  of  power,  and  consequently  of  speed,  can  be  secured  by 


110 


LOCOMOTIVE  PERFORMANCE 


manipulating  the  reverse-lever  of  this  locomotive.  Quadrants  of  the 
modern  locomotive  are,  however,  much  more  closely  notched,  and  as, 
in  present-day  practice,  locomotives  are  allowed  to  go  as  fast  as 
they  will  whatever  load  may  be  attached  to  them,  the  question 
outlined  now  has  much  less  significance  than  formerly. 

37.  The  Steam  Consumption  per  horse-power  hour  for  different 
speeds  and  cut-offs  is  shown  numerically  by  Fig.  65  and  graphically 


55-fMin  -[Ho] 


Cut-Off 


Reverse  Lever  Notch 


FIG.  65. — Steam  per  I.H.P.  per  Hour. 

by  Fig.  66.  Engineers  unfamiliar  with  the  performance  of  the  loco- 
motive have  often  characterized  it  as  an  extremely  wasteful  engine, 
whereas  from  Fig.  65  it  appears  that  its  performance  compares  favor- 
ably with  that  of  any  other  class  of  single-cylinder,  non-condensing 
engine.  With  open  throttle,  the  consumption  of  steam  per  indicated 
horse-power  does  not  under  any  conditions  of  speed  or  cut-off  exceed 
32  pounds,  and  under  favorable  conditions  it  falls  to  about  26  pounds. 
In  this  connection  it  should  be  noted  that  Schenectady  No.  1  carried 
but  140  pounds  pressure,  and  that  the  tests  were  run  at  about  130. 
When  favored  by  a  higher  pressure,  this  engine  has  given  one  horse- 


CHANGES  IN  SPEED  AND   CUT-OFF. 


Ill 


power  on    a    consumption  of  less   than   25  pounds    of    steam  per 
hour. 

The  results  show  that  the  minimum  consumption  is  obtained  at  the 
35  per  cent  cut-off,  or,  say,  one-third  stroke ;  this  for  an  engine  carrying 
140  pounds  of  steam.  The  losses  resulting  from  the  employment  of  a 
shorter  cut-off  are,  however,  slight  as  compared  with  those  which  attend 
a  lengthening  of  the  cut-off.  An  exception  to  this  statement  isr 
however,  to  be  found  at  high  speed,  where  the  25  per  cent  cut-off  is 


FIG.  66. — Steam  per  I.H.P.  per  Hour. 

better  than  the  35  per  cent.  It  should  be  said,  also,  that  experiments 
involving  higher  steam  pressures  go  to  show  that  the  most  economical 
cut-off  for  all  speeds  is  somewhere  between  one-quarter  and  one-third 
stroke.  It  appears,  also,  whatever  may  be  the  cut-off,  that,  beginning 
with  slow  motion,  a  gradual  increase  of  speed  is  attended  by  a  de- 
crease in  the  amount  of  steam  required  up  to  a  certain  point,  after 
which  the  consumption  increases.  Both  an  inspection  of  the  values 
of  Fig.  65  and  a  glance  at  the  curves  of  Fig.  66  show  the  most  economi- 


112  LOCOMOTIVE  PERFORMANCE. 

cal  performance  to  have  been  obtained  at  a  speed  of  but  35  miles 
per  hour,  or  188  revolutions  per  minute.  In  explanation  of  this  fact, 
it  would  appear  that  below  this  limit  any  increase  of  speed  is  of  advan- 
tage through  reduced  cylinder  condensation,  an  advantage  which  is 
roften  assumed  to  attend  all  increase  of  piston  speed,  but  above  this 
limit  some  other  influence  enters  which  is  so  strong  in  its  effect  as  to 
more  than  neutralize  the  advantage  of  the  higher  piston  speed.  This 
neutralizing  influence  is  without  doubt  the  wiredrawing,  the  presence 
of  which  becomes  more  and  more  marked  as  the  speed  rises. 

38.  Critical  Speed. — In  the  two  paragraphs  immediately  preceding, 
attention  has  been  called  to  the  fact  that  the  maximum  power  and 
the  maximum  efficiency  of  locomotive  Schenectady  No.  1  were  found 
at  a  speed  of  approximately  35  miles  an  hour,  or  190  revolutions  per 
minute.     To  give  significance  to  the  conditions  involved,  the  author 
has  called  that  speed  at  which  the  power  and  efficiency  of  a  locomotive 
become  maximum  the  " critical  speed."     It  will,  of  course,  not  always 
be  found  at  35  miles  an  hour,  for  much  depends  upon  the  diameter 
of  drivers,  but  it  will  be  found  not  far  from  200  revolutions  per  minute. 
With  higher  steam  pressures  the  limit  is  probably  raised  somewhat, 
.and  with  a  superior  valve-gear  the  point  may  not  be  quite  so  well 
marked  as  in  the  data,  but  the  preceding  statement  will  be  found 
substantially  true  in  its  application  to  all  simple  locomotives. 

39.  Cylinder   Condensation. — The  effect  of  changes  in  speed  and 
fcut-off  upon  the  percentage  of  the  total  steam  used,  which  is  shown 
rby  the  indicator,  is  given  by  Fig.  67.     Two  facts  are  clearly  presented 
iby  this  figure.     The  first  is  that  the  percentage  of  the  steam  used 
-which  is  accounted  for  by  the  indicator,  is  greatest  at  the  critical  speed. 
This  appears   to  be  true  for  all  cut-offs.     The  data  well  illustrate  a 
rather  commonly  accepted  theory,  that  for  a  given  cut-off  anything 
~which  tends  to  suppress  cylinder  condensation  improves  the  perform- 
ance of  the  engine.     Fig.  67  shows  that  either  increasing  the  speed 
.above  or  diminishing  it  below  35  miles  an  hour  increases  the  conden- 
sation, and  it  has  already  been  shown  (Fig.  65)  that  similar  changes 
operate  to  increase  the  water  consumption  of  the  engine. 

A  second  fact,  which  is  apparent  from  Fig.  67,  is  that  at  constant 
^speed  any  increase  of  cut-off  increases  the  percentage  of  steam  shown 
by  the  indicator,  or  diminishes  the  condensation.  The  data  show 
some  exceptions  to  this  rule,  but  they  involve  values  which  are  small. 
The  tendency  of  the  exhibit  is  clear.  It  will  be  elsewhere  shown 
(throttling  test,  Chapter  XX.)  that  by  throttling  and  making  the 


CHANGES  IN  SPEED  AND  CUT-OFF. 


113 


cut-off  very  late  in  the  stroke  more  than  90  per  cent  of  all  the  steam 
used  is  shown  by  the  indicator. 

Dealing  with  the  more  detailed  action  which  marks  the  inter- 
change of  heat  between  the  steam  and  the  walls  of  the  cylinder,  atten- 
tion is  first  called  to  the  percentage  of  mixture  present  as  steam  at 
cut-off.  (Fig.  68.)  The  difference  between  the  values  given  and  100 
will  represent  the  percentage  of  the  mixture  which  is  water.  Here 


Reverse  Lever  Notch 


FIG.  67. — Percentage  of  Total  Steam  shown  by  Indicator. 

again,  it  appears  that  at  any  given  cut-off  the  percentage  of  the  mixture 
which  is  present  as  steam  is  nowhere  greater  than  at  the  critical  speed. 
Other  values  of  interest  are  shown  by  Table  XXIII.  Thus,  the  last- 
four  columns  of  this  table  show  the  extent  of  the  reevaporation  during 
expansion  when  the  cut-off  is  constant.  This  reevaporation  in  all 
cases  increases  with  increase  of  speed,  while  at  constant  speed  length- 
ening the  cut-off  diminishes  the  reevaporation.  For  example,  referring 
to  the  25-mile  series,  the  test  with  the  reverse-lever  in  the  first  notch 
gave  a  reevaporation  per  revolution  of  .0148;  with  the  reverse-lever 


114 


LOCOMOTIVE  PERFORMANCE. 


in  the  second  notch  the  reevaporation  decreased  to  .0045  pound; 
and  with  the  reverse-lever  in  the  third  notch  all  reevaporation  dis- 
appeared, and  the  condensation  amounted  to  .0167  pound. 

The  weight  of  mixture  in  the  cylinder  per  revolution  and  the 
weight  exhausted  (Table  XXIII.)  shows,  when  compared,  the  char- 
acter of  the  exhaust  action  at  different  speeds.  For  example,  refer- 
ring to  the  series  for  which  the  reverse-lever  was  in  the  first  notch, 
at  15  miles  an  hour,  of  the  1.4  pounds  in  the  cylinder,  1.1  pounds 


cs  per  Hour 

Revolutions  per  Minute 

35 

80.1 

79.4 

o 

» 

43 

79.9 

81.2 

42 

4 

33 

80.1 

KB  4 

81.6 

, 

i 

S8 

1 

i 

25 

76.4 

80.3 

79.5 

i 

35 

g 

I 

13 

72.2 

77.0 

Si- 

25 

35 

45 

p 

jrqen 

of  Stroke 

2 


Reverse  Lever  Notch 


3 

Cut-Off 
FIG.  68. — Percentage  of  Total  Steam  shown  by  Indicator  at  Cut-off. 

were  exhausted,  leaving  0.30  of  a  pound  during  compression.  When 
the  speed  is  increased  to  55  miles  per  hour,  of  the  0.88  of  a  pound 
in  the  cylinder,  but  0.49,  or  a  trifle  more  than  half,  is  exhausted. 
It  is,  however,  worthy  of  note  that  while  the  relative  amount  of 
mixture  retained  during  compression  is  much  greater  at  the  higher 
speed,  the  actual  increase  is  small  since  the  weight  of  mixture  during 
compression  at  the  higher  speed  is  but  0.39. 

A  more  detailed  exhibit  of  data  derived  from  these  tests,  relating 
to  the  interchange  of  heat,  will  be  found  in  Chapter  IV.,  Series  A. 


CHANGES  IN  SPEED  AND  CUT-OFF. 


115 


TABLE  XXIII. 

THERMAL  ACTION  WITHIN  THE  CYLINDERS. 


Designa- 
tion of 
Test. 

Weight  of 
Mixture  in 
Cylinder  per 
Revolution. 

Lbs. 

Weight  of 
Mixture 
Exhausted 
per 
Revolution. 

Lbs. 

Reevaporation. 

Condensation. 

Per 
Revolution. 

Lbs. 

Per 
I.H.P.  per 
Hour. 
Lbs. 

Per 

Revolution. 

Lbs. 

Per 
I.H.P.  per 
Hour. 
Lbs. 

15-1-A 
25-1  -A 
35-1-A 
45-1-A 
55-1-A 

15-2-A 
25-2-A 
35-2-A 
45-2-A 
55-2-A 

1.4166 
1.0834 
1.0456 
0.9465 

0.8848 

1.1369 
0.7816 
0.7071 

0.5787 
0.4862 

0.0106 
0.0148 
0.0182 
0.0118 
0.0237 

0.3994 
0.5307 
0.7071 
0.5859 
1.4929 

.7828 
.5006 
.3026 
.1818 
.1406 

1.5692 
1.2555 
1.0016 
0.8432 
0.7636 

0^0045 
0.0155 
0.0146 
0.0220 

6!o96i 

0.4063 
0.4921 
0.9233 

0.0108 

0.1903 

25-3-A 
35-3-A 

.8863 
.6626 

1.6663 
1.3528 

0^0081 

0^1802 

0.0167 

0.2646 

40.  Boiler  Performance. — Since  the  performance  of  the  boiler  is 
fully  treated  in  another  portion  of  this  work,  it  is  unnecessary  to 
present  an  elaborate  discussion  in  this  connection.  It  will,  however, 
serve  in  the  further  discussion  of  the  performance  of  the  locomotive, 
if  some  attention  be  given  the  limitation  upon  its  capacity.  This  is 
well  set  forth  in  Fig.  69.  The  values  of  this  figure  show  the  pounds 
of  water  from  and  at  212  degrees,  which  were  required  to  be  evapo- 
rated each  hour  to  sustain  the  operation  of  the  locomotive  under  the 
conditions  of  speed  and  cut-off  indicated.  The  values  on  shaded 
background  represent  an  hourly  evaporation  of  more  than  12;500 
pounds,  and  correspond  to  a  rate  of  power  which  approaches  closely 
to  the  maximum  of  the  boiler  when  fired  with  Indiana  block  coal. 
With  a  better  fuel  it  is  probable  that  a  total  of  18,000  can  be  evapo- 
rated, an  amount  which  is  equal  to  15  pounds  of  water  per  foot  of 
heating  surface  per  hour.  Accepting  this  latter  value  as  representing 
the  maximum  capacity  of  the  boiler,  then  the  points  of  cut-off  and 
speed,  for  which  the  boiler  will  serve  to  meet  the  demands  of  the 
cylinders  under  a  fully  open  throttle,  will  be  represented  by  the 
curve  in  Fig.  69.  Thus,  at  25  miles  steam  can  be  supplied  for  a 
cut-off  of  over  55  per  cent;  while  at  a  speed  of  50  miles  the  cut-off 
cannot  be  much  greater  than  45  per  cent.  An  attempt  to  employ 
longer  cut-offs  will  result  in  failure  through  lack  of  steam.  This  curve 


116 


LOCOMOTIVE  PERFORMANCE. 


represents  maximum  performance,  under  a  wide-open  throttle,  for 
the  engine  in  question.  It  shows,  also,  the  effect  of  changes  in  speed 
upon  the  total  consumption.  Thus,  comparing  tests  for  which  the 
cut-off  is  the  same,  it  will  be  seen  that  the  demand  upon  the  boiler 
is  not  greatly  increased  by  increasing  the  speed.  The  reason  for  this 
has  already  been  explained,  but  it  will  be  of  interest  to  note  that 
the  upper  portion  of  the  curve  of  maximum  performance  is  so  nearly 
vertical  that,  after  the  speed  has  reached  25  miles,  but  slight  reduc- 


Reverse  Lever  Notch 


'FiG.  69. — Equivalent  Evaporation  per  Hour. 

tions  in  the  cut-off  are  required  to  enable  the  boiler  to  meet  the 
demands  of  the  cylinders  under  further  increments  of  speed.  Doub- 
ling the  speed  from  25  miles  to  50  miles  only  requires  the  cut-off  to 
be  reduced  from  55  per  cent  to  45  per  cent;  whereas,  if  it  were  not  for 
the  wire-drawing  action,  it  might  be  expected  that  doubling  the  speed 
would  necessitate  the  use  of  half  the  cut-off. 

The  pounds  of  water  evaporated  per  pound  of  coal,  as  actually 
obtained  for  the  tests,  are  given  by  the  points  in  Fig.  70,  and,  as 
rectified  by  the  use  of  the  equation 

E=  10.08  -.296H. 


CHANGES  IN  SPEED   AND  CUT-OFF. 


117 


by  the  line  in  the  same  figure.  A  full  statement  of  observed  and  cal- 
culated data,  derived  from  the  boiler  as  a  result  of  the  twelve  tests 
under  consideration,  will  be  found  in  the  recorded  data,  Chapter  IV. 

41.  Performance  of  the  Locomotive  as  a  Whole.  —  Dealing 
first  with  the  locomotive  as  a  power-plant,  consisting  of  boiler  and 
engines,  its  performance  is  briefly  set  forth  by  Table  XXIV.  and 
Fig.  71.  From  these  exhibits  it  appears  that  an  indicated  horse- 
power is  under  most  conditions  of  operation  obtained  on  a  consump- 


i  11 


10 


I  3 

I 


1          2          3          4          5          6          7          8          9         10        11        12        13 
"    Equivalent  Evaporation  per  Sq.  Ft.  Heating  Surface  per  Hour 


14 


FIG.  70. — Evaporative  Efficiency. 

tion  of  from  4  to  6  pounds  of  Brazil  block  coal.  With  higher  grades 
•of  coal  it  should  be  possible  to  lower  the  record  by  about  one-fifth, 
making  the  range  3.2  to  4.8  pounds.  These  latter  values  may  fairly 
be  used  in  comparing  the  performance  of  a  simple  locomotive  opera- 
ting under  ordinary  conditions  with  steam-plants  of  other  types. 
The  rate  at  which  power  is  developed  is  well  shown  by  the  table 
Each  foot  of  heating  surface  in  the  boiler  yields  from  .15  to  .47  of  a 
horse-power,  and  each  foot  of  grate  surface  from  11  to  28  horse- 
power. Results  which  will  approach  these  in  value  are  not  to  be 
found  in  any  other  class  of  service. 


118 


LOCOMOTIVE  PERFORMANCE. 


TABLE  XXIV. 
BOILER  AND  ENGINE  PERFORMANCE. 


Coal  per  I.H.P. 

Indicated  Horse-power 

Designation  of 

per  Hour. 

Test. 

Lbs. 

Per  Square  Foot  of 
Heating  Surface. 

Per  Square  Foot  of 
Grate  Surface. 

15-1-A 

4.16 

0.157 

10.90 

25-1-A 

4.05 

0.178 

12.40 

35-1-A 

4.19 

0.248 

17.23 

45-1-A 

4.52 

0.249 

17.27 

55-1-A 

4.87 

0.239 

16.63 

15-2-A 

4.16 

0.226 

14.99 

25-2-A 

4.40 

0.297 

20.65 

35-2-A 

4.67 

0.357 

24.87 

45-2-A 

5.26 

0.359 

25.01 

55-2-A 

6.40 

0.361 

25.03 

25-3-A 

5.41 

0.370 

25.80 

35-3-A 

6.25 

0.407 

28.31 

TABLE  XXV. 

PERFORMANCE  AT   THE  DRAW-BAR. 


Designation  • 
of  Test. 

Steam  Used 
per  D.H.P. 
per  Hour. 

Lbs. 

Dry  Coal  Used 
per  D.H.P. 
per  Hour. 

Lbs. 

Dynamometer  Horse-power 

Per  Square  Foot 
of  Heating 
Surface. 

Per  Square  Foot 
of  Grate 
Surface. 

15-1-A 
25-1-A 
35-1-A 
45-1-A 
55-1-A 

32.92 
33.87 
32.93 
37.45 
43.86 

4.69 
4.90 
5.14 
5.95 
7.01 

0.138 
0.148 
0.203 
0.190 
0.167 

9.7 
10.4 
-     14.3 
13.4 
11.8 

15-2-A 
25-2-A 
35-2-A 
45-2-A 
55-2-A 

29.64 
28.91 
29.18 
32.59 
38.03 

4.48 
.     4.77 
5.19 
6.06 
7.59 

0.202 
0.274 
0.322 
0.315 
0.304 

14.2 
19.3 
22.7 
22.1 
21.3 

25-3-A 
35-3-A 

30.27 
32.44 

5.77 
6.79 

0.351 
0.379 

24.7 
26.7 

Between  the  cylinders  and  the  draw-bar  there  is,  of  course,  some 
loss  of  power  (Chapter  XIX.),  which,  in  the  case  of  a  locomotive  on  a 
testing-plant,  amounts  only  to  the  friction  of  the  machine.  Since, 
however,  it  is  the  whole  purpose  of  a  locomotive  to  exert  force  at 


CHANGES  IN  SPEED  AND  CUT-OFF. 


119 


the  draw-bar,  it  is  of  importance  to  possess  some  measure  of  its  per- 
formance in  terms  of  force  exerted  at  the  draw-bar.  Table  XXV. 
gives  a  record  of  the  weight  of  steam  and  coal  used  per  hour  in 
developing  a  horse-power  at  the  draw-bar.  The  coal  used  is  also 
shown  diagrammatically  by  Fig.  72.  The  table  gives  also  the  horse- 
power developed  at  the  draw-bar  (dynamometer  horse-power)  per 
foot  of  heating  surface  and  per  foot  of  grate  surface  respectively. 


2  3  Reverse  Lever  Notch 

Cut-Off 
FIG.  71.— Coal  per  I.H.P.  per  Hour. 

The  effective  pull  exerted  at  the  draw-bar  is  shown  by  Fig.  73 
and  the  equivalent  horse-power  by  Fig.  74.  The  horse-power  equiva- 
lent to  machine  friction  is  shown  by  Fig.  75.  A  correct  understand- 
ing of  the  general  effect  of  increments  of  speed  upon  the  forces  exerted 
at  the  draw-bar  is  a  matter  of  great  importance  to  any  one  inter- 
ested in  locomotive  performance.  The  effects  are  so  well  shown  by 
the  figures  referred  to  as  to  make  them  well  worthy  of  careful  study. 
The  coal  used  per  mile  run  is  shown  by  Fig.  76. 

42.  Maximum  Power  Dependent  upon  Efficiency.  —  It  has 
already  been  stated  that  anything  which  operates  to  increase  the 


LOCOMOTIVE  PERFORMANCE. 


3 
Cut-Off 


Reverse  Lever  Notch 


FIG.  72. — Coal  per  D.H.P.  per  Hour. 


Miles  per  Hour 

Ti 

1342 

2431 

£ 

1870 

3132 

e 

40 

2600 

4157 

5050 

88 

>JU 

n^ 

2793 

5259 

6&66 

i 

ao 

~<J 

1  "i 

4180 

6409 

01 

s 

5 

3 

5 

4 

r> 

1 

I'er 

?.er 

t< 

f  S 

tr( 

ke 

3 

Cut-Off 
FIG.  73.— Draw-bar  Pull. 


Reverse  Lever  Notch 


CHANGES  IN  SPEED  AND  CUT-OFF. 


121 


Reyolutions  pe^JMinute 

203.4 

368.6 

%") 

oc 

5-j 

T 

IB 

230.9 

382.0 

JO 

^ 

MS 

246.0 

391.4 

459.9 

1 

10 

OB 

179.3 

332.6 

426.5 

j 

JB 

l  ~, 

167.2 

244.9 

gl 

2 

\ 

8 

I 

4 

5 

Iferpetit  ojf  S,trc 

ke 

1                           2              -            3                            Reverse  Lever  Notch 
Cut-Off 

FIG.  74. — Dynamometer  Horse-power. 


87.7  H~ 


69.5 


71.4 


55.8 


35 


54.8 


43.1 


35.6 


-188 


* 


37.1 


28.9 


25.0 


135 


23.1 


17.5 


81 


25 


35 


45 


Percent  of  Stroke 


2  3 

Cut-Off 

FIG.  75. — Friction  Horse-power. 


Reverse  Lever  Motch 


122 


LOCOMOTIVE  PERFORMANCE. 


efficiency  of  a  locomotive  may,  at  the  normal  limit  of  power,  be 
utilized  in  the  development  of  more  power.  The  importance  of  this 
statement  entitles  it  to  some  further  consideration. 

It  is  evident  that  the  maintenance  of  pressure  in  the  cylinders 
demands  steam  from  the  boiler,  and,  hence,  that  the  limit  of  cylinder 
work  is  reached  when  the  boiler  can  no  longer  meet  the  demand 
which  is  made  upon  it.  If  now  some  improvement  in  fire-box  or 


;        3  .    Reverse  Lever  Notch 

Cut-Off 
FIG.  76.— Coal  per  Mile  Run. 

boiler  construction  is  adopted  which  will  increase  the  evaporative 
efficiency  of  the  boiler,  making  it  possible  to  evaporate  more  water 
in  return  for  each  pound  of  fuel  burned,  then,  at  the  sacrifice  of 
the  saving,  it  will  become  possible  to  establish  a  new  and  a  higher 
limit  in  the  capacity  of  the  boiler.  The  more  efficient  boiler  can 
be  made  to  deliver  more  steam,  which,  in  turn,  may  be  utilized  in 
the  development  of  more  power. 

Again,  assuming  the  boiler  performance  to  remain  unchanged, 
an  improvement  in  the  cylinder  action  will  be  found  to  give  a  simi- 
lar result.  For  example,  with  a  definite  maximum  quantity  of 


CHANGES  IN  SPEED  AND  CUT-OFF.  123 

steam,  the  cylinders  under  normal  conditions  can  deliver  a  certain 
maximum  power.  If  now,  by  the  adoption  of  compound  cylinders, 
or  of  some  other  improvement,  an  arrangement  can  be  had  which 
delivers  a  horse-power  upon  the  consumption  of  less  steam  than 
before,  then  the  definite  maximum  quantity  of  steam  which  can  be 
delivered  by  the  boiler  will  not  be  entirely  consumed  in  developing 
the  normal  cylinder  power,  and  the  surplus  can  be  employed  in 
developing  more  power. 

In  a  similar  manner  it  can  be  shown  that  any  improvement 
which  will  increase  the  efficiency  of  any  essential  detail  of  the  machine 
establishes  a  credit  which,  when  the  locomotive  is  pushed  to  its  high- 
est performance,  may  be  invested  in  an  increase  of  power. 

There  is,  therefore,  a  twofold  purpose  to  be  served  by  any  device 
or  arrangement  which  adds  to  the  efficiency  of  any  important  ele- 
ment of  the  locomotive:  first,  under  normal  conditions  of  opera- 
tion, that  of  saving  fuel,  and,  second,  when  the  need  is  for  the  largest 
possible  output  of  work,  that  of  raising  the  maximum  output  of 
power. 


III.  THE  BOILER. 


CHAPTER  VT. 

BOILER   PERFORMANCE.* 

43.  Selection  of  Data.— The  tabulated  data  in  Chapter  IV.  con- 
stitute the  results  obtained  from  forty-four  efficiency  tests  of  the 
experimental  locomotive.  It  will  be  noted  that  the  first  thirty-five 
tests  were  all  made  within  a  period  of  two  years  between  November 
23,  1894,  and  February  11,  1897.  The  discussion  in  this  chapter 
is  based  on  these  thirty-five  tests.  Other  tests  were  made  earlier 
and  later  than  these,  and  some  of  the  earlier  results  were  published ;  f 
but  inasmuch  as  the  earlier  results  were  for  the  most  part  obtained 
at  a  time  when  the  mounting  mechanism  of  the  testing-plant  was 
being  perfected,  and  when  the  accessory  apparatus  for  detecting 
errors  was  limited,  they  do  not  possess  the  same  degree  of  reliability 
as  those  chosen  for  the  present  purpose.  During  .the  early  existence 
of  the  plant  the  conditions  affecting  the  operation  of  the  boiler  could 
not  be  maintained  with  the  same  degree  of  constancy  as  was  after- 
ward possible,  and,  to  add  to  the  irregularities,  different  men  were 
employed  in  firing,  which  as  a  study  of  the  results  has  shown,  intro- 
duced a  personal  variable.  The  results  of  a  considerable  number  of 
later  tests  were  destroyed  by  fire. 

The  analysis  which  follows  will  show  that  the  experimental 
results  are  in  most  respects  consistent.  Some  of  the  facts  which 
at  first  appear  to  be  irregular  will  be  accounted  for,  while  others 

*  This  discussion  was  presented  as  a  paper  before  the  American  Society  of  Mechan- 
ical Engineers  in  December,  1900,  forming  part  of  Vol.  XXII  of  the  Transactions. 

f  Tests  of  the  Locomotive  at  the  Laboratory  of  Purdue  University,  Trans.  M.  E., 
Vol.  XIV. 

124 


BOILER   PERFORMANCE.  125 

must  be  passed  over  as  at  present  impossible  of  explanation.  It 
is  probable,  however,  that  a  full  knowledge  of  all  the  conditions 
affecting  the  performance  of  the  locomotive  boiler  may  serve  to> 
make  clear  those  phenomena  which  are  at  present  inexplicable. 

44.  The  Boiler. — A    complete    description   of    the    boiler   under 
consideration,  together  with  a  statement  of  all  dimensions,  will  be 
found  presented  in  Chapter  III.     The  boiler,  during  its  stay  in  the 
laboratory,   suffered   little  or   no   change  of   condition.     The   water 
used  carries  some  solid  matter  in  solution,  but  it  does  not  form  hard 
scales,  unless  it  is  allowed  to  remain  in  the  boiler  for  a  considerable 
period.      The  boiler  of  Schenectady  was   never  neglected,   and  at 
the  close  of  its  service  in  the  laboratory  it  was  clean  and  otherwise 
in  as  good  condition  as  when  work  was  commenced  upon  it. 

45.  General  Conditions  (Table    XXVI). — To   those   accustomed 
to  reviewing  data  derived  from  stationary  boilers,  the  duration  of 
the  tests  (Column  4)  will  appear  insufficient.     The  arguments  sus- 
taining the  practice  involving  short  tests  for  locomotives  on  a  test- 
ing-plant  were  presented   to   the   committee   having   in   charge   the 
revision   of   the   American    Society   of   Mechanical    Engineers'    code 
relative  to  a  standard   method  of  conducting   boiler-tests,  and  will 
be  found  in  the  published  correspondence  of  that  committee.*     The 
tests  herein  recorded  were  run  several  years  in  advance  of  the  presen- 
tation of  the  committee's  final  report,  and  for  this  reason  it  will  be 
of  interest  to  call  attention  to  the  fact  that  fifteen  out  of  the  thirty- 
five  tests  perfectly  fulfill  the  requirements  of  the  present  code.     In 
defense  of  those  which  are  shorter  than  allowed  by  the  code,  it  should 
be  said  that  the  writer's  opinion  on  the  subject  was  embodied  in  a 
recommendation  to  the  committee  to  the  effect  that  the  limit  apply- 
ing in  such  cases  be  the  burning  of  a  total  for  the  test  of  not  less 
than  100  pounds  of  coal  per  foot  of  grate  surface.     The  committee 
adopted   the  general   form   of   the   recommendation,   but   fixed   the 
limit  at  250  pounds.     For  two  of  the  tests  presented  the  total  fuel 
per  foot  of  grate  is  slightly  below  150  pounds,  and  for  four  others 
it  is  below  200. 

The  boiler  pressure  (Column  5)  was  practically  the  same  for  afT 
tests  save  two,  and  for  these  it  was  intentionally  higher  than  the  nor- 
mal in  the  one  case  and  lower  in  the  other.  Pressures  were  observed 
from  an  ordinary  dial-gauge  at  five-minute  intervals,  and  also  recorded 

*  Proceedings  Am.  Soc.  Mech.  Eng'rs,  Vol.  XXI,  p.  112. 


126 


LOCOMOTIVE  PERFORMANCE. 


TABLE  XXVI. 
GENERAL  CONDITIONS. 

The  several  tests  represented  in  this  table  are  arranged  in  order  of  the  rate  of 
evaporation,  No.  1  representing  the  test  for  which  the  rate  is  least,  and  No.  35 
that  for  which  it  is  greatest. 


Identification  of  Test. 

Average  Pressure,  Pounds 
per  Square  Inch. 

Average  Temp., 
Deg.  Fahr. 

Dura- 

tion of 

tt 

Test  in 

Consecuti 
Numbe 

Labora- 
tory 
Designa- 
tion. 

Date  of  Test. 

Min- 
utes. 

Steam 
Pressure 
in  Boiler 
by  Gauge. 

Atmos- 
pheric 
Pressure. 

Absolute 
Steam 
Pressure. 

Of 
Labora- 
tory. 

Of 
Feed- 
water. 

1 

2 

3 

4 

5 

6 

7 

8 

9 

1 

15-1-A 

Dec.   12,  1894 

240 

125.9 

14.5 

140.4 

65 

53.2 

2 

15-U-V 

Nov.  23,  1894 

190 

127.3 

14.5 

141.8 

74 

53.8 

3 

15-1-H 

Dec.     9,  1896 

180 

123.6 

14.3 

137.9 

72 

54.6 

4 

25-1  -A 

Dec.   14,  1894 

255 

120.1 

14.5 

134.6 

67 

53.8 

5 

15-1  G 

Nov.     9,  1896 

180 

123.6 

14.4 

138.0 

69 

53.3 

6 

15-2-  A 

Nov.  13,  1895 

180 

129.5 

14.4 

143.9 

79 

55.2 

7 

25-1-V 

Nov.  26,  1894 

240 

127.1 

14.3 

141.4 

70 

53.9 

8 

35-1-A 

Dec.   17/1894 

180 

129.7 

14.6 

144.3 

75 

53.2 

9 

35-2-F 

Jan.    21,  1895 

180 

155.4 

14.7 

170.1 

71 

52.7 

10 

35-1-V 

Dec.     7,  1894 

140 

128.9 

14.3 

143.2 

69 

51.9 

11 

35-2-E 

Jan.    16,  1895 

180 

128.1 

14.5 

142.6 

71 

51.9 

12 

45-1-  A    ;  Nov.  20,  1895 

150 

128.8 

14.3 

143.1 

76 

56.4 

13 

35-2-B 

Jan.    14,  1895 

170 

98.4 

14.4 

112.8 

66 

50.0 

14 

55-1-A 

Nov.  25,  1895 

120 

124.9 

14.2 

139.1 

76 

56.0 

15 

35-1-H 

Dec.   18,  1896 

160 

121.2 

14.6 

135.8 

67 

52.6 

16 

35-1-G 

Nov.  20,  1896 

170 

125.0 

14.6 

139.6 

74 

55.0 

17 

35-1&-G 

Dec.     2,  1896 

170 

128.2 

14.6 

142.8 

78 

52.5 

18 

25-2-A 

Oct.    25,  1895 

180 

129.3 

14.4 

143.7 

85 

56.0 

19 

55-1-V 

Dec.   18,  1895 

120 

128.4 

14.4 

142.8 

76 

58.1 

20 

35-26-H 

Feb.   10,  1897 

160 

122.6 

14.5 

137.1 

74 

50.6 

21 

55-1-H 

Feb.   11,  1897 

120 

127.5 

14.4 

141.9 

71 

52.1 

22 

55-1-G 

Nov.  23,  1896 

120 

126.9 

14.5 

141.4 

79 

54.2 

23 

15-9-  A 

Nov.    6,  1896 

150 

122.5 

14.3 

136.8 

79 

55.6 

24 

15-9-H 

Dec.   11,  1896 

180 

122.7 

14.4 

137.1 

81 

53.2 

25 

35-2-A 

Dec.    19,  1894 

180 

123.0 

14.5 

135.7 

72 

52.5 

26 

35-3-G 

Dec.     4,  1896 

140 

125.9 

14.3 

140.2 

70 

52.6 

27 

15-9-G 

Nov.  12,  1896 

160 

124.1 

14.5 

138.6 

77 

53.1 

28 

35-3-H 

Dec.   14,  1896 

120 

116.5 

14.3 

130.8 

73 

53.0 

•29 

35-2-G 

Nov.  13,  1896 

160 

121.0 

14.5 

135.5 

78 

53.6 

30 

35-2-H 

Dec.   16,  1896 

120 

112.0 

14.6 

126.6 

72 

53.0 

31 

45-2-A 

Nov.  18,  1895 

140 

126.7 

14.3 

141.0 

84 

55.0 

32 

25-3-A 

Nov.     1,  1895 

122.5 

127.2 

14.5 

141.7 

76 

53.3 

33 

35-2-C 

Jan.    23,  1895 

120 

143.3 

14.4 

157.7 

71 

51.7 

34 

55-2-A 

Nov.  22,  1895 

68 

124.0 

14.4 

138.4 

76 

58.4 

35 

35-3-A 

Nov.  15,  1895 

120 

125.3 

14.3 

139.6 

77 

55.5 

BOILER  PERFORMANCE. 


127 


by  a  Bristol  gauge.  To  better  show  the  fluctuations  in  pressure, 
the  chart  of  this  and  other  recording-gauges  used  about  the  loco- 
motive  had  a  rapid  motion,  making  a  complete  revolution  in  six 
hours.  A  sample  chart  is  presented  as  Fig.  77. 

46.    Actual    Evaporation    (Table    XXVII).  — This    table   shows 
(Columns  10  and  11)  the  regularity  with  which  water  was  delivered 


FIG.  77. — Chart  from  Recording-gauge  showing  Boiler  Pressure. 

to  the  boiler;  the  total  pounds  delivered  to  the  injector  during  the 
test  (Column  12);  the  pounds  caught  from  injector  overflow  (Column 
13) ;  the  pounds  received  by  the  boiler  (Column  14) ;  and  the  rate 
at  which  the  evaporation  proceeded  (Column  15).  In  all  tests  an 
effort  was  made  to  keep  the  injector  constantly  in  action,  but  for 
those  of  low  power  the  rate  of  delivery  could  not  be  made  sufficiently 
small  to  permit  this  being  done.  The  data  for  a  few  of  the  tests 
show  the  injector  to  have  been  started  two  or  more  times,  while  its 


128 


LOCOMOTIVE  PERFORMANCE. 


TABLE  XXVII. 
ACTUAL  EVAPORATION. 

The  several  tests  represented  in  this  table  are  arranged  in  order  of  the  rate  of 
evaporation,  No.  1  representing  the  test  for  which  the  rate  is  least,  and  No.  35 
that  for  which  it  is  greatest. 


Identification 

Water  and  Steam. 

of  Test. 

Consecutive 
Number. 

Labora- 
tory 
Designa- 
tion. 

Dura- 
tion of 
Test  in 
Min- 
utes. 

Number 
of 
Times 
Injector 
was 
Started. 

Minutes 
One  or 
Both  In- 
jectors 
were  in 
Action. 

Total 
Pounds  of 
Water 
Delivered 
to  In- 
jectors. 

Pounds  of 
Water 
Lost  from 
Injector 
Overflow. 

Pounds  of 
Water  De- 
livered to 
Boiler  and 
Presum- 
ably Evap- 
orated. 

Pounds  of 
Water 
Evap- 
orated 
per  Hour. 

1 

2 

4 

10 

11 

12 

13 

14 

15 

1 

15-1-A 

240 

22 

130 

22,415 

315 

22,100 

5,525 

2 

15-1  &-V 

190 

14 

129 

17,925 

135 

17,790 

5,618 

3 

15-1-H 

180 

7 

126 

18,349 

126 

18,223 

6,075 

4 

25-1-A 

255          10 

236 

25,9.35 

100 

25,895 

6,093 

5 

15-1-G 

180 

12 

127 

18.768 

72 

18.696 

6.232 

6 

15-2-A 

180 

9 

149 

21,885 

44 

21,841 

7,280 

7 

25-1-V 

240 

7 

213 

29,508 

32 

29,476 

7,369 

8 

35-1-A 

180 

2 

180 

24,468 

100 

24,368 

8,123 

9 

35-2-F 

180 

9 

149 

24,793 

460 

24,333 

8,111 

10 

35-1-V 

140 

1 

136 

19,899 

0 

19,899 

8,528 

11 

35-2-E 

180 

3 

175 

25,742 

45 

25,697 

8,566 

12 

45-1-A 

150 

2 

146 

21,688 

15 

21,673 

8,669 

13 

35-2-B 

170 

8 

158 

24,728 

173 

24,555 

8,666 

14 

55-1-A 

120 

1 

120 

17,970 

87 

17,883 

8,941 

15 

35-1-H 

160 

1 

160 

24,793 

70 

24,723 

9,271 

16 

35-1-G 

170 

1 

170 

26.598 

35 

26,563 

9,375 

17 

35-1  b-G 

170 

1 

170 

26,753 

10 

26,743 

9.439 

18 

25-2-A 

180 

1 

180 

28,911 

5 

28,906 

9,635 

19 

55-1-V 

120 

1 

120 

19,526 

108 

19,418 

9.709 

20- 

35-26-H 

160 

1 

160 

25,834 

5 

25,829 

9,686 

21 

55-1-H 

120 

1 

120 

20,514 

0 

20,514 

10,257 

22 

55-1-G 

120 

1 

120 

20.791 

30 

20,761 

10,381 

23 

15-9  A 

150 

1 

150 

28,582 

60 

28,522 

11,409 

24 

15-9-H 

180 

1 

180 

34,403 

30 

34,373 

11,458 

25 

35-2-A 

180 

1 

180 

34,351 

29 

34,325 

11,442 

26 

35-3-G 

140 

1 

140 

27,060 

0 

27,060 

11,597 

27 

15-9-G 

160 

1 

154 

30,877 

5 

30,872 

11,577 

28 

35-3-H 

120 

1 

120 

23,446 

60 

23,386 

11,693 

29 

35-2-G 

160 

1 

160 

32,886 

40 

32,846 

12,317 

30 

35-2-H 

120 

3 

115 

24,793 

60 

24,733 

12,367 

31 

45-2-A 

140 

1 

140 

29,313 

213 

29,100 

12,472 

32 

25-3-A 

122 

1 

122 

26,415 

14 

26,401 

12,931 

33 

35-2-C 

120 

3 

120 

26,034 

25 

26,009 

13,004 

34 

55-2-A 

68 

1 

68 

16,188 

277 

15,911 

14,039 

35 

35-3-A 

120 

1 

120 

29,984 

109 

29,875 

14,937 

BOILER  PERFORMANCE  129 

period  of  action  is  recorded  as  coincident  with  the  length  of  the  test. 
This  apparent  inconsistency  is  explained  by  the  fact  that  it  was 
sometimes  convenient  to  change  from  one  injector  to  the  other 
during  the  progress  of  the  tests,  and  at  other  times  both  injectors 
were  in  action  at  the  same  time.  Column  10  merely  shows  the 
number  of  starts  made,  and  includes  the  record  for  both  injectors. 
The  last  column  of  this  table  discloses  something  of  the  significance 
of  the  conditions  attending  the  action  of  the  locomotive  boiler.  For 
example,  test  35  shows  that  nearly  15,000  pounds  of  water  were 
delivered  to  the  boiler  and  presumably  evaporated  each  hour,  or, 
approximately,  250  pounds  per  minute.  This  rate  of  very  nearly 
a  barrel  a  minute  is  sufficient  to  evaporate  an  amount  of  water  equal 
to  the  full  water  capacity  of  the  boiler  in  34  minutes.  At  this  rate, 
had  the  injectors  ceased  in  their  action,  the  water  level  would  have 
fallen  between  the  upper  and  the  middle  gauges  at  the  rate  of  one 
inch  each  minute. 

47.  Quality  of  Steam  and  Equivalent  Evaporation  (Table 
XXVIII). — The  quality  of  steam,  assuming  dry  saturated  steam 
to  be  unity,  is  shown  by  Column  16,  and  the  percentage  of  moisture 
by  Column  17.  Results  were  obtained  by  the  use  of  a  throttling 
calorimeter  of  an  approved  form,  taking  steam  from  a  perforated 
pipe  extending  horizontally  into  the  dome  of  the  boiler  at  a  point  A, 
Fig.  35  (Chapter  III.) ,  near  the  throttle-opening.  Observations  were 
made  at  five-minute  intervals.  An  examination  of  the  table  will  show , 
that,  in  general,  the  amount  of  moisture  in  the  steam  increases  as  the 
rate  of  evaporation  is  increased,  though  variations  in  individual  results 
are  so  great  that  they  do  not  fall  in  any  well-defined  line.  The  reason 
for  apparent  inconsistencies  is  to  be  looked  for  either  in  the  methods 
employed,  or  in  actual  variations  in  the  performance  of  the  boiler. 
The  methods  employed  were  the  same  for  all  tests,  while  the  condition 
of  the  boiler  was  necessarily  subject  to  change.  The  boiler  had  to 
be  frequently  washed.  It  is  conceivable  that  dryer  steam  may  be 
furnished  by  the  boiler  when  newly  washed  than  when  in  a  condition 
requiring  washing,  though  there  is  nothing  in  the  data  either  to 
sustain  or  to  discredit  such  a  conclusion.  It  has,  however,  been 
shown  by  Professor  Jacobus  *  that  almost  all  moisture  which  may 
be  intermixed  with  steam  passing  a  horizontal  pipe  separates  itself 

*  Tests  to  show  the  Distribution  of  Moisture  in  Steam  when  flowing  in  a  Hori- 
zontal Pipe,  Transactions  of  the  American  Society  of  Mechanical  Engineers,  Vol.  XVI, 
p  1017. 


130 


LOCOMOTIVE  PERFORMANCE. 


TABLE  XXVIII. 
QUALITY  OF  STEAM  AND  EQUIVALENT  EVAPORATION. 

The  several  tests  represented  in  this  table  are  arranged  in  order  of  the  rate  of 
evaporation,  No.  1  representing  the  test  for  which  the  rate  is  least,  and  No.  35 
that  for  which  it  is  greatest. 


Identification  of 
Test. 

Results  of  Calorimeter 
Tests. 

Equivalent  Evaporation 
from  and  at  212°  Fahr.  per 
Hour. 

Dura- 
tion of 
Test  in 

Quality  of 
Steam  in 

Assuming 

Assuming  all 
Water  Deliv- 

Consec- 
utive 

Labora- 
tory 

Min- 
utes. 

Dome  of 
Boiler,  Dry, 

Percentage 
of  Moisture 

Quality  of 
Steam  as 

ered  to  Boiler 
to  have  been 

Num- 

Desig- 

Saturated 

in  Steam. 

Shown  by 

Completely 

ber. 

nation. 

Steam  being 

Column  16. 

Evaporated 

Taken  as 

into  Dry 

.  Unity. 

Steam. 

1 

2 

4 

16 

17 

18 

19 

1 

15-1-A 

240 

.9951 

0.49 

6,659 

6,683 

2 

15-U-V 

190 

.9937 

0.63 

6,763 

6,794 

3 

15-1-H 

180 

.9838 

1.62 

7,249 

7,337 

4 

25-1-A 

255 

.9922 

0.78 

7,318 

7,360 

5 

15-1-G 

180 

.9894 

1.06 

7,476 

7,535 

6 

15-2-A 

180 

.9924 

0.76 

8,745 

8,796 

7 

25-1-V 

240 

.9932 

0.68 

8,865 

8,910 

8 

35-1-A 

180 

.9917 

0.83 

9,771 

9,832 

9 

35-2-F 

180 

.9900 

1.00 

9,785 

9,855 

10 

35-1-V 

140 

.9937 

0.63 

10,284 

10,332 

11 

35-2-E 

180 

.9932 

0.68 

10,324 

10,377 

12 

45-1-A 

150 

.9913 

0.87 

10,395 

10,463 

13 

35-2-B 

170 

.9931 

0.69 

10,413 

10,467 

14 

55-1-A 

120 

.9878 

1.22 

10,691 

10,788 

15 

35-1-H 

160 

.9851 

1.49 

11.090 

11,214 

16 

35-1-G 

170 

.9886 

1.14 

11,226 

11,322 

17 

35-1  6-G 

170 

.9860 

1.40 

11,312 

11,430 

18 

25-2-A 

180 

.9910 

0.90 

11,554 

11,633 

19 

55-1-V 

120 

.9912 

0.88 

11,624 

11,700 

20 

35-2&-H 

160 

.9880 

1.20 

11,634               11,737 

21 

55-1-H 

120 

.9871 

1.29 

12,303 

12,422 

22 

55-1-G 

120 

.9869 

1.31 

12,426 

12,548 

23 

15-9-A 

150 

.9906 

0.94 

13,670 

13,766 

24 

15-9-H 

180 

.9871 

.29 

13,722              13,853 

25 

35-2-A 

180 

.9894 

.06 

13,735              13,843 

26 

35-3-G 

140 

.9838 

.62 

13,867              14,035 

27 

15-9-G 

160 

.9871 

.29 

13,869               14,002 

28 

35-3-H 

120 

.9873 

.27 

13,995               14,128 

29 

35-2-G 

160 

.9856 

.44 

14,725               14,884 

30 

35-2-H 

120 

.9866 

.34 

14,771 

14,932 

31 

45-2-A 

140 

.9876 

.24 

14,926 

15,065 

32 

25-3-A 

122.5 

.9889 

.11 

15,515 

15,644 

33 

35-2-C 

120 

.9930 

.70 

15,709 

15,788 

34 

55-2-A 

68 

.9887 

.13 

16,773 

16,903 

35 

35-3  -A 

120 

.9889 

.11 

17,883 

18,032 

BOILER  PERFORMANCE.  131 

from  the  steam  by  gravitation,  and  forms  a  rill  in  the  bottom  of  the 
pipe,  the  steam  above  being  approximately  dry.  Experiments  by 
the  writer,  involving  a  visual  examination  of  the  steam-space  of  a 
boiler  while  in  action,  revealed  no  haze  or  mist  above  the  surface  of 
the  water,  thus  sustaining  the  conclusion  that  the  steam  writhin  the 
steam-space  of  the  boiler  is  ordinarily  dry  and  saturated;  the  water 
is  present  as  water  and  the  steam  as  steam.  They  are  not  intermixed. 
If  this  is  true,  the  steam  which  passes  the  throttle  cf  a  locomotive 
should  be  expected  to  be  dry,  and  it  would  be  entirely  so  if  it  were 
not  that  the  violence  of  the  circulation  projects  small  beads  of  water 
upward,  far  beyond  the  general  surface.  Some  of  these  enter  the 
throttle  with  the  steam.  This  action  explains  why  the  moisture 
increases  with  the  power  of  the  boiler,  and  makes  it  not  unreasonable 
to  assume  that  the  purity  of  the  water  in  the  boiler  may  actually 
affect  the  quality 'of  the  steam. 

The  comparative  dryness  of  the  steam  under  all  conditions  is  a 
fact  worthy  of  emphasis,  for  the  locomotive  is  often  credited  with 
carrying  over  a  great  deal  of  water  to  the  cylinders.  The  tests  show 
that  this  does  not  happen  under  constant  conditions  of  running. 
When  it  occurs  it  is  probably  the  result  of  too  high  a  water  level 
or  of  a  sudden  demand  upon  the  boiler.  For  example,  if  the  throttle 
of  a  locomotive,  which  has  been  for  some  time  inactive,  is  quickly 
opened,  large  volumes  of  steam-bubbles  leave  the  heating  surface  and 
crowd  to  the  upper  part  of  the  boiler,  making  spray  in  the  dome,  a 
portion  of  which  may  pass  out  with  the  steam.  A  similar  action 
occurs  when  an  engine,  which  has  been  working  at  a  light  load,  is 
suddenly  required  to  increase  its  power.  But  these  are  exceptional 
conditions.  Under  uniform  conditions  of  running,  such  as  prevailed 
throughout  the  tests  herein  presented,  the  moisture  passing  the 
throttle  is  never  great. 

If,  as  the  writer  believes,  it  is  fair  to  conclude  that  variations  in 
moisture  are  largely  due  to  incidental  conditions,  no  serious  mistake 
would  be  made  if  the  indications  of  the  calorimeter  were  entirely 
disregarded,  and  all  calculations  based  on  the  assumption  that  the 
steam  generated  is  dry  and  saturated.  Results  thus  obtained  should 
be  somewhat  more  consistent,  one  with  another,  than  those  cor- 
rected for  moisture,  and  hence  for  general  purposes  more  satisfactory. 
In  accord  with  this  view,  while  none  of  the  calorimeter  work  has  been 
ignored  in  calculating  results,  many  of  the  derived  results  have  been 
carried  out  in  duplicate.  Thus,  the  equivalent  evaporation  is  first 


132  LOCOMOTIVE  PERFORMANCE. 

determined  on  the  assumption  that  the  steam  has  the  quality  shown 
by  the  calorimeter  (Column  18),  and  is  also  determined  on  the  assump- 
tion that  all  water  delivered  to  the  boiler  is  evaporated  into  dry 
and  saturated  steam  (Column  19).  In  accord  with  the  usual  practice, 
however,  comparisons  which  follow  are  based  on  the  corrected  results 
(Column  18). 

48.  Power  of  Boiler  (Table  XXIX)  .—The  power  developed  by  the 
boiler  is  proportional  to  the  rate  of  evaporation  (Column  18).     A 
few  comparisons  will  serve  to  show  something  of  the  peculiar  con- 
ditions under  which  the  boiler  of  a  locomotive  performs  its  service. 
Thus,  the  water  evaporated  per  foot  of  grate  surface  (Column  20) 
varies  from  less  than  400  to  more  than  1,000  pounds  per  hour.     These 
figures  reflect  well  the  intensity  of  the  furnace  action,  which  must 
provide  for  the  combustion  of  sufficient  fuel  to  produce  such  a  result. 
Similarly,  the  weight  of  water  evaporated  per  square  foot  of  heating 
surface  (Column  21)  varies  from  5J  to  almost  15  pounds  per  hour,  the 
maximum  rate  being  nearly  the  equivalent  of  a  boiler  horse-power 
for  every  2  square  feet  of  heating  surface  in  the  boiler.     The  total 
boiler  horse-power  (Column  22),  the  horse-power  per  square  foot  of 
heating  surface  (Column  23),  and  the  horse-power  per  square  foot 
of  grate  surface  (Column  24)  are  also  of  interest,  especially  for  the 
higher  power  tests. 

49.  Coal  and   Combustible   (Table  XXX). — Attention  has  been 
called  to  the  very  large  amount  of  water  evaporated  by  the  boiler 
tested.     It  follows  that  a  correspondingly  large  amount  of  fuel  is 
needed  to  bring  about  this  evaporation.    .The  record  appears  in  Table 
XXX. 

The  coal  used  for  all  tests  was  Indiana  block,  mined  in  the  neigh- 
borhood of  Brazil.  It  burns  to  a  white  ash,  without  clinkers,  and  is 
light  and  friable,  which  qualities  prevent  its  giving  maximum  results 
in  locomotive  service.  The  composition  of  several  representative 
samples  proved 'to  be  as  follows: 

1334 

Per  cent  fixed  carbon 49.65          51.84          51.09          51.59 

Per  cent  volatile  matter 40.29          39.00          38.93          38.87 

Per  cent  combined  moisture 3. 15  3.62  2.35  3.44 

Per  cent  ash 6.91  5.54  7.63  6.10 

100.00    100.00    100.00    100.00 

In  each  test  the  coal  was  weighed — a  barrowful  at  a  time — as  it 
was  dumped  at  the  feet  of  the  fireman.  A  sample  of  from  50  to  100 


BOILER   PERFORMANCE. 


133 


TABLE  XXIX. 
POWER. 

The  several  tests  represented  in  this  table  are  arranged  in  order  of  the  rate  of 
evaporation,  No.  1  representing  the  test  for  which  the  rate  is  least,  and  No.  35 
that  for  which  it  is  greatest. 


Identification 
of  Test. 

Dura- 

Equivalent Evaporation  from  and 
at  212°  Fahr.  Pounds,  assuming 
Quality  of  Steam    as   shown  by 
Column  16. 

Rated  Horse-power  34.5 
Evaporative  Units,  assuming 
Quality  of  Steam  as  shown 
by  Column  16. 

tion  of 

Test  in 

Water 

Water 

>nsecutive 
Number. 

Labora- 
tory 
Desig- 
nation. 

Min- 
utes. 

Water 
Hour. 

Evaporated 
per  Square 
Foot  of 
Grate 
Surface 

Evaporated 
per  Square 
Foot  of 
Heating 
Surface 

Total. 

5er  Square 
Foot  of 
Heating 
Surface. 

Per  Square 
Foot  of 
Grate 
Surface. 

a 

per  Hour. 

per  Hour. 

i 

2 

4 

18 

20 

21 

22 

23 

34 

i 

15-1-A 

240 

6,659 

386 

5.48 

193 

.159 

11.2 

2 

15-1  6-V 

190 

6,763 

392 

5.57 

196 

.161 

11.4 

3 

15-1-H 

180 

7,249 

420 

5.97 

210 

.173 

12.2 

4 

25-1-A 

255 

7,318 

424 

6.03 

212 

.175 

12.3 

5 

15-1-G 

180 

7,476 

433 

6.16 

217 

.179 

12.6 

6 

15-2-  A 

180 

8,745 

507 

7.20 

253 

.208 

14.7 

7 

25-1-V 

240 

8,865 

514 

7.30 

257 

.212 

14.8 

8 

35-1-A 

180 

9,771 

566 

8.05 

283 

.233 

16.4 

9 

35-2-F 

180 

9,785 

567 

8.06 

284 

.234 

16.4 

10 

35-1-V 

140 

10,284 

596 

8.47 

298 

.245 

17.3 

11 

35-2-E 

180 

10,324 

598 

8.51 

299 

.246 

17.3 

12 

45-1-A 

150 

10,395 

603 

8.56 

301 

.248 

17.4 

13 

35-2-B 

170 

10,413 

604 

8.57 

302 

.249 

17.5 

14 

55-1-A 

120 

10,691 

619 

8.80 

310 

.255 

17.9 

15 

35-1-H 

160 

11,090 

643 

9.13 

321 

.264 

18.6 

16 

35-1-G 

170 

11,226 

650 

9.24 

325 

.268 

18.8 

17 

35-1  &-G 

170 

11,312 

655 

9.31 

328 

.270 

19.0 

18 

25-2-A 

180 

11,554 

669 

9.51 

335 

.276 

19.4 

19 

55-1-V 

120 

11,624 

673 

9.57 

337 

.278 

19.5 

20 

35-2&-H 

160 

11,634 

674 

9.58 

337 

.278 

19.5 

21 

55-1-H 

120 

12,303 

713 

10.13 

357 

.294 

20.7 

22 

55-1-G 

120 

12,426 

720 

10.23 

360 

.296 

20.9 

23 

15-9-  A 

150 

13,670 

792 

11.25 

396 

.326 

22.9 

24 

15-9-H 

180 

13,722 

796 

11.29 

398 

.328 

23.1 

25 

35-2-A 

180 

13,735 

796 

11.31 

398 

.328 

23.1 

26 

35-3-G 

140 

13,867 

804 

11.42 

402 

.331 

23.3 

27 

15-9-G 

160 

13,869 

804 

11.42 

402 

.331 

23.3 

28 

35-3-H 

120 

13,995 

811 

11.52 

406 

.334 

23.5 

29 

35-2-G 

160 

14,725 

853 

12.12 

427 

.352 

24.8 

30 

35-2-H 

120 

14,771 

856 

12.16 

428 

.353 

24.8 

31 

45-2-A 

140 

14,926 

865 

12.29 

433 

.357 

25.1 

32 

25-3-A 

122.5 

15,515 

899 

12.77 

450 

.370 

26.1 

33 

35-2-C 

120 

15,709 

911 

12.93 

455 

.375 

26.4 

34 

55-2-A 

68 

16,773 

973 

13.81 

486 

.400 

28.2 

35 

35-3-A 

120 

17,883 

1,037 

14.93 

518 

.427 

30.0 

134 


LOCOMOTIVE  PERFORMANCE. 


TABLE  XXX. 
COAL  AND  COMBUSTION. 

The  several  tests  represented  in  this  table  are  arranged  in  order  of  the  rate  of 
evaporation,  No.  1  representing  the  test  for  which  the  rate  is  least,  and  No.  35 
that  for  which  it  is  greatest. 


Identification 

Fuel:  Indiana  Brazil  Block  Coal,  Pounds. 

Rate  of  Com- 

of Test. 

bustion. 

Dura- 

8,31 1 

ls§ 

|| 
1* 

Labora- 
tory 
Desig- 
nation. 

tion  of 
Test  in 
Min- 
utes. 

Total 
Dry 
Coal 
Fired. 

Total 
Refuse 
Caught 
in  Ash- 
pan. 

Total 
Com- 
bustible 
by 

Analy- 
sis. 

Dry 

Coal 
Fired 

Hour. 

Com- 
bustible 
Fired 

Hour. 

y  Coal  Fired 
3q.  Ft.  of  Gn 
Surface  per  H 

y  Coal  Fired 
!q.  Ft.of  Heat 
Surface  per  H 

Q 

»_i/j<Ai 
Q 

1 

2 

4 

27 

28 

29 

30 

31 

32 

33 

1 

15-1-A 

240 

3,399 

292 

3,059 

850 

765 

49.3 

.700 

2 

15-1&-V 

190 

2,577 

261 

2,319 

814 

732 

47.2 

.670 

3 

15-1-H 

180 

2,375 

240 

2,138 

792 

713 

45.9 

.652 

4 

25-1-A 

255 

3,864 

93 

3,478 

909 

818 

52.8 

.748 

5 

15-1-G 

180 

2,678 

262 

2,410 

893 

803 

51.8 

.735 

6 

15-2-A 

180 

3,297 

258 

2,967 

1,099 

989 

63.7 

.905 

7 

25-1-V 

240 

4,460 

320 

4,014 

1,115 

1,003 

64.6 

.918 

8 

35-1-A 

180 

3,785 

299 

3,406 

1,262 

1,135 

73.1 

1.038 

9 

35-2-F 

180 

3,859 

295 

3,473 

1,286 

1,158 

74.6 

.059 

10 

35-1-V 

140 

3,180 

272 

2,862 

1,363 

1,227 

78.9 

.122 

11 

35-2-E 

180 

4,107 

353 

3,696 

1,369 

1,232 

79.3 

.127 

12 

45-1-A 

150 

3,272 

231 

2,945 

1,309 

1,178 

75.9 

.078 

13 

35-2-B 

170 

4,370 

461 

3,933 

1,542 

1,388 

89.4 

.270 

14 

55-1-  A 

120 

2,980 

220 

2,682 

,490 

1,341 

86.4 

.227 

15 

35-1-H 

160 

4,152 

320 

3,737 

,557 

1,401 

90.3 

.283 

16 

35-1-G 

170 

4,288 

342 

3,859 

,513 

1,362 

87.7 

.246 

17 

35-1  6-G 

170 

4,150 

380 

3,735 

,465 

1,318 

84.9 

.206 

18 

25-2-A 

180 

4,826 

25 

4,343 

,609 

1,448 

93.3 

.324 

19 

55-1-V 

120 

3,330 

239 

2,997 

,665 

1,498 

96.5 

.371 

20 

35-26-H 

160 

4,321 

332 

3,889 

,620 

1,458 

93.9 

.334 

21 

55-1-H 

120 

3,203 

214 

2,883 

,602 

1,441 

92.8 

.319 

22 

55-1-G 

120 

3,769 

241 

3,392 

1,885 

1,696 

109.2 

.552 

23 

15-9-  A 

150 

5,014 

265 

4,513 

2,006 

1,805 

116.3 

.651 

24 

15-9-H 

180 

6,363 

344 

5,727 

2,121 

1,909 

123.0 

.746 

25 

35-2-A 

180 

5,933 

258 

5,339 

1,978 

1,780 

114.6 

.628 

26 

35-3-G 

140 

4,708 

365 

4,237 

2,018 

1,816 

117.0 

.662 

27 

15-9-G 

160 

5,487 

354 

4,938 

2,058 

1,852 

119.3 

.694 

28 

35-3-H 

120 

4,248 

346 

3,823 

2,124 

1,912 

123.2 

.749 

29 

35-2-G 

160 

6,183 

363 

5,565 

2,319 

2,087 

134.4 

.909 

30 

35-2-H 

120 

4,250 

297 

3,823 

2,125 

1,912 

123.2 

1.750 

31 

45-2-A 

140 

5,720 

243 

5,148 

2,452 

2,206 

142.1 

2.019 

32 

25-3-A 

122. 

4,684 

91 

4,216 

2,294 

2,065 

133.0 

1.889 

33 

35-2-C 

120 

5,356 

384 

4,820 

2,678 

2,410 

155.3 

2.205 

34 

55-2-A 

68 

2,995 

205 

2,643 

2,695 

2,378 

153.2 

2.176 

35 

35-3-A 

120 

6,266 

298 

5,639 

3,133 

2,819 

181.6 

2.581 

BOILER  PERFORMANCE.  135 

pounds  was  put  into  a  large  galvanized  iron  pan,  and  air-dried.  From 
results  thus  obtained,  the  total  weight  of  coal  fired  was  corrected  for 
accidental  moisture,  giving  results  which  appear  in  Column  27.  As 
the  coal  was  stored  under  roof,  the  correction  was  always  small. 

The  total  weight  of  dry  coal  fired,  as  given  for  the  several  tests 
(Column  27),  contains  two  variables:  the  length  of  the  test  and  the 
rate  of  combustion.  The  values  given  as  dry  coal  fired  per  hour 
(Column  30)  eliminate  the  first  variable,  and  supply  a  true  basis  from 
which  to  compare  the  rates  of  combustion  incident  to  the  several 
tests.  It  will  be  seen  that  the  amount  of  coal  fired  per  hour  is  between 
the  limits  of  792  pounds  and  3,133  pounds.  Five  tests  have  a  rate 
of  less  than  J  a  ton  per  hour,  and  twelve  have  a  greater  rate  than  1 
ton  per  hour.  The  rate  per  square  foot  of  grate  per  hour  (Column  32) 
ranges  from  46  to  182,  values  the  significance  of  which  appears  when 
it  is  considered  that  even  in  naval  service,  under  forced  draft,  the 
rate  seldom  exceeds  60  pounds  per  hour.  The  coal  burned  per  foot 
of  heating  surface  per  hour  (Column  33)  varies  from  .7  to  2.6  pounds. 

The  amount  of  refuse  caught  in  the  ash-pan  (Column  28)  is  an 
item  of  no  great  importance  in  the  case  of  locomotive  boilers,  since 
a  large  amount  of  non-combustible  material  which  would,  under  the 
conditions  of  stationary  practice,  lodge  in  the  ash-pan  is,  in  locomotive 
service,  thrown  out  at  the  top  of  the  stack.  The  proportion  of  the 
whole  amount  of  ash  contained  by  the  fuel  which  appears  in  the  ash- 
pan  depends  upon  the  force  of  the  draft,  or,  in  other  words,  upon 
the  rate  of  power  at  which  the  boiler  is  worked.  It  is  greatest  when 
the  rate  of  combustion  is  least.  When  the  engine  is  worked  at  very 
high  power,  the  amount  of  refuse  in  the  ash-pan,  with  the  light  fuel 
employed  in  the  tests  under  consideration,  is  almost  negligible. 

In  stationary  practice  the  total  combustible  (Column  29)  is  ob- 
tained by  subtracting  the  weight  of  refuse  from  the  weight  of  coal. 
For  reasons  already  explained,  such  a  process  gives  no  useful  result 
when  applied  to  the  tests  of  locomotive  practice.  For  the  present 
purpose,  therefore,  resort  has  been  had  to  the  chemical  analysis  of 
the  fuel,  which  shows  about  one-tenth  the  weight  of  the  dry  coal 
to  be  non-combustible.  The  total  combustible  is  therefore  assumed 
to  equal  nine-tenths  of  the  weight  of  dry  coal  fired.  The  combustible 
per  hour  on  this  basis  is  shown  as  Column  31. 

50.  Thermal  Units  (Table  XXXI).— The  thermal  units  imparted 
to  each  pound  of  water  passing  the  boiler,  or 

Q  =  xr  +  q  -  q0, 


136 


LOCOMOTIVE  PERFORMANCE. 


TABLE  XXXI. 

THERMAL  UNITS. 

The  several  tests  represented  in  this  table  are  arranged  in  order  of  the  rate  of 
evaporation,  No.  1  representing  the  test  for  which  the  rate  is  least,  and  No.  35 
that  for  which  it  is  greatest. 


Identification  of  Test. 

Duration  of 

British  Thermal  Units.    Assuming  Steam  to  have  the 
Quality  as  shown  by  Column  16. 

Test  in 

Consecu- 
tive 
Number. 

Laboratory 
Designation. 

Minutes. 

Per  Pound 
of  Steam 
Generated. 

Total  per 
Minute. 

Per  Pound 
of  Dry 
Coal. 

Per  Pound 
of  Com- 
bustible. 

1 

2 

4 

34 

35 

36 

37 

1 

15-1-A 

240 

1,164.1 

107,194 

7,569 

8,410 

2 

15-1  &-V 

190 

1,162.6 

108,858 

8,026 

8,918 

3 

15-1-H 

180 

1,152.4 

116,668 

8,842 

9,823 

4 

25-1-A 

255 

1,160.0 

117,798 

7,774 

8,638 

5 

15-1-G 

180 

1,158.6 

120,340 

8,088 

8,988 

6 

15-2-A 

180 

1,160.2 

140,778 

7,686 

8,541 

7 

25-1-V 

240 

1,161.8 

142,688 

7,678 

8,531 

8 

35-1-A 

180 

,161.7 

157,268 

7,479 

8,310 

9 

35-2-F 

180 

,165.1 

157,502 

7,348 

8,163 

10 

35-1-V 

140 

,164.7 

165,546 

7,288 

8,098 

11 

35-2-E 

180 

,164.1 

166,188 

7,283 

8,093 

12 

45-1-A 

150 

,158.1 

167,336 

7,671 

8,523 

13 

35-2-B 

170 

1,160.5 

167,624 

6,521 

7,245 

14 

55-1-A 

120 

1,154.7 

172,079 

6,729 

7,699 

15 

35-1-H 

160 

1,155.3 

178,516 

6,879 

7,643 

16 

35-1-G 

170 

1,156.5 

180,706 

7,164 

7,961 

17 

35-1  6-G 

170 

,157.4 

182,072 

7,458 

8,287 

18 

25-2-A 

180 

,158.2 

185,994 

6,937 

7,709 

19 

55-1-V 

120 

,156.3 

187,109 

6,743 

7,492 

20 

35-2&-H 

160 

,160.0 

187,260 

6,934 

7,704 

21 

55-1-H 

120 

,158.5 

198,046 

7,419 

8,243 

22 

55-1-G 

120 

,156.1 

200,015 

6,369 

7,076 

23 

15-9-A 

150 

,157.2 

220,038 

6,583 

7,314 

24 

15-9-H 

180 

,156.6 

220,866 

6,248 

6,942 

25 

35-2-A 

180 

,159.3 

221,092 

6,707 

7,452 

26 

35-3-G 

140 

,154.8 

223,206 

6,637 

7,375 

27 

15-9-G 

160 

1,157.0 

223,243 

6,510 

7,234 

28 

35-3-H 

120 

1,155.9 

225,266 

6,363 

7,071 

29 

35-2-G 

160 

1,154.6 

237,025 

6,134 

6,815 

30 

35-2-H 

120 

,153.5 

237,746 

6,713 

7,459 

31 

45-2-A 

140 

,155.9 

240,262 

5,881 

6,534 

32 

25-3-A 

122 

,158.8 

249,743 

6,531 

7,256 

33 

35-2-C 

120 

,166.7 

252,873 

5,666 

6,296 

34 

55-2-A 

68 

,153.9 

269,996 

6,130 

6,812 

35 

35-3-A 

120 

,156.3 

287,871 

5,513 

6,126 

are  given  in  Column  34.  The  rate  at  which  heat  is  transferred,  as 
indicated  by  the  thermal  units  absorbed  by  the  water  of  the  boiler 
each  minute,  is  given  in  Column  35,  while  the  thermal  units  absorbed 


BOILER  PERFORMANCE.  137 

per  pound  of  dry  coal  burned  are  given  in  Column  36,  and  per  pound 
of  combustible  in  Column  37. 

No  attempt  has  been  made  to  express  in  numerical  terms  the 
thermal  efficiency  of  the  boiler.  The  determination  of  such  a  value 
depends  upon  the  heating  value  of  the  fuel,  which  is  not  known  in 
precise  terms.  It  is  probably  not  far  from  13,000  thermal  units  per 
pound  of  dry  coal.  Comparing  this  value  with  the  number  of  thermal 
units  taken  up  by  the  water  of  the  boiler  for  each  pound  of  coal  burned 
(Column  36),  an  approximate  estimate  of  the  thermal  efficiency  of 
the  boiler  may  be  had. 

While  the  facts  presented  by  this  table  are  especially  for  the  con- 
venience of  those  who  may  desire  to  compare  the  performance  of  the 
boiler  tested  with  data  from  other  boilers,  they  are  not  without  inter- 
est in  themselves.  For  example,  it  is  of  interest  to  see  that  in  test 
No.  35  the  boiler  transmitted  approximately  288,000  thermal  units 
per  minute.  That  is,  it  delivered  heat  sufficient  to  raise  the  tempera- 
ture of  144  tons  of  water  one  degree  every  minute.  As  many  loco- 
motives are  now  in  service  having  more  than  double  the  power  of 
the  one  tested,  it  may  be  said  that  the  modern  locomotive  is  capable 
of  delivering  sufficient  heat  to  raise  300  tons  of  water  one  degree  in 
temperature  each  minute. 

51.  Draft,  Rate  of  Combustion,  and  Smoke-box  Temperature 
(Table  XXXII). — For  the  present  purpose  draft  is  defined  as  the 
difference  between  the  pressure  of  the  atmosphere  and  that  of  the 
smoke-box.  The  draft-gauge  consists  of  a  U  tube  partially  filled 
with  water,  and  securely  attached  to  a  pillar  of  the  laboratory. 
One  leg  of  the  tube  is  in  pipe  connection  with  the  interior  of  the 
smoke-box,  the  opening  being  at  the  point  C,  Fig.  35,  and  on  the 
axis  of  the  boiler.  Observations  were  made  at  five-minute  intervals. 
For  the  tests  reported,  the  average  draft  (Column  38)  varies  from 
1.7  inches  to  7.5  inches. 

In  any  boiler  the  condition  of  draft  determines  the  rate  of 
combustion,  and  consequently,  under  ideal  conditions,  the  draft  will 
be  a  function  of  the  rate  of  combustion.  But  under  conditions 
actually  affecting  the  action  of  the  boiler  of  a  locomotive  there  are 
variations  in  this  relationship.  The  precise  action  of  the  steam- 
jet  in  producing  a  draft  action  has  been  discussed  in  another 
place.*  It  is  shown  elsewhere  in  this  discussion  f  that,  other  things 

*  Report  of  Committee  on  "Exhaust-pipes  and  Steam-passages.        Proceedings 
of  the  American  Railway  Master  Mechanics'  Association,  1896. 
t  Chapter  XI. 


138 


LOCOMOTIVE  PERFORMANCE 


TABLE  XXXII. 
DRAFT,  RATE  OF  COMBUSTION,  AND  SMOKE-BOX  TEMPERATURE. 

The  several  tests  represented  in  this  table  are  arranged  in  order  of  the  rate  cf 
evaporation,  No.  1  representing  the  test  for  which  the  rate  is  least,  and  No.  35 
that  for  which  it  is  greatest. 


Identification  of  Test. 

Duration  of 
Test  in 
Minutes. 

Average  Pres- 
sure.    Draft, 
or  Vacuum,  in 
Smoke-box, 
Inches  of 
Water. 

Average 
Temperature, 
Deg.  Fahr., 
of 
Smoke-box. 

Fuel:  Indiana 
Brazil  Block 
Coal,  Pounds. 
Dry  Coal 
Fired  per 
Hour. 

Consecu- 
tive 
Number. 

Laboratory 
Designation. 

1 

2 

4 

38 

39 

40 

1 

15-1-A 

240 

1.72 

553 

850 

2 

15-1  6-V 

190 

2.04 

550 

814 

3 

15-1-H 

180 

1.93 

570 

792 

4 

25-1-A 

255 

1.93 

567 

909 

5 

15-1-G 

180 

1.87 

583 

893 

6 

15-2-A 

180 

2.42 

621 

1,099 

7 

25-1-V 

240 

2.60 

606 

1,115 

8 

35-1-A 

180 

3.00 

628 

1,262 

9 

35-2-F 

180 

2.57 

653 

1,286 

10 

35-1-V 

140 

3.43 

633 

1,363 

11 

35-2-E 

180 

2.89 

652 

1,369 

12 

45-1-A 

150 

2.68 

644 

1,309 

13 

35-2-B 

170 

3.28 

664 

1,542 

14 

55-1-A 

120 

2.58 

675 

1,490 

15 

35-1-H 

160 

3.00 

655 

1,557 

16 

35-1-G 

170 

3.02 

685 

1,513 

17 

35-1  6-G 

170 

2.98 

618 

1,465 

18 

25-2-A 

180 

3.37 

696 

1,609 

19 

55-1-V 

120 

3.20 

667 

1,665 

20 

35-26-H 

160 

3.18 

689 

1,620 

21. 

55-1-H 

120 

3.44 

695 

1,602 

22 

55-1-G 

120 

3.57 

1,885 

23 

15-9-A 

150 

4.56 

724 

2,006 

24 

15-9-H 

180 

4.99 

696 

2,121 

25 

35-2-A 

180 

4.42 

720 

1,978 

26 

35-3-G 

140 

4.88 

719 

2,018 

27 

15-9-G 

160 

4.76 

724 

2,058 

28 

35-3-H 

120 

4.52 

2,124 

29 

35-2-G 

160 

4.65 

655 

2,319 

30 

35-2-H 

120 

4.33 

2,125 

31 

45-2-A 

140 

4.93 

74i 

2,452 

32 

25-3-A 

122.5 

5.45 

762 

2,294 

33 

35-2-C 

120 

5.13 

738 

2,678 

34 

55-2-A 

68 

4.58 

755 

2,695 

35 

35-3-A 

120 

7.48 

798 

3,133 

being  equal,  the  capacity  of  the  jet  as  a  means  for  producing  draft 
is  nearly  proportional  to  the  weight  of  steam  discharged  per  unit 
of  time;  and  that,  whether  the  discharge  is  in  the  slow,  heavy  puffs  inci- 


BOILER  PERFORMANCE. 


139 


dent  to  slow  speed,  or  in  lighter  but  more  rapid  impulses,  is  not 
material.  If  the  weight  of  steam  discharged  is  the  same,  the  draft 
action  is  approximately  constant.  The  reduction  of  pressure  in 
the  smoke-box,  however,  which  may  result  from  the  action  of  the 


FIG.  78. — Chart  from  Recording-gauge  showing  Draft. 

This  and  other  charts  from  recording-gauges  are  from  test  No.  12.  The  test 
began  with  a  flying  start  at  1.45.  The  normal  draft  from  the  test  was  a  little 
less  than  3  inches  (exactly  2.68  inches).  Where  the  line  rises  above  this  value  it 
indicates  that  the  dampers  were  closed,  and  where  it  falls  below,  that  the  fire-door 
was  open.  So  far  as  the  record  shows  the  frequency  with  which  the  dampers  were 
changed,  it  is  an  unusual  one.  Referring  to  the  diagrams  of  other  gauges  (Figs.  77 
and  79),  the  constancy  of  steam  pressure  and  of  draft  may  be  judged. 

exhaust  under  given  conditions,  depends  upon  the  freedom  with 
which  air  is  permitted  to  pass  into  the  fire-box.  If  the  fire  is  thick 
and  solid,  the  draft,  as  determined  by  the  reduction  of  pressure 
in  the  smoke-box,  will  be  high;  if  the  fire  is  light,  the  draft  will 


140 


LOCOMOTIVE  PERFORMANCE. 


be  low.  This  is  well  shown  by  Fig.  78,  which  is  a  representative 
diagram  from  the  registering  vacuum-gauge  connected  with  the 
smoke-box.  The  normal  draft  is  shown  to  be  approximately  three 
inches.  When  the  fire-door  is  opened  the  draft  drops,  though  the 
scale  at  which  Fig.  78  is  reproduced  does  not  permit  this  to  be  well 
shown,  When  the  ash-pan  dampers  are  closed  the  draft  goes  above 


FIG.  79. — Chart  from  Recording-gauge  showing  Back  Pressure  in 
Exhaust-passage  in  Saddle. 

the  normal.  The  draft  readings  given  (Column  38)  are  the  average 
results  of  observations  at  five-minute  intervals.  They  may  be  ac- 
cepted as  a  close  approximation  to  the  normal  readings  for  the  tests. 
The  relation  of  reduction  of  pressure  in  the  smoke-box  to  coal 
burned  per  square  foot  of  grate  surface  is  well  shown  by  Fig.  80, 
and  the  relation  of  pressure  reduction  in  smoke-box  to  evaporation 


BOILER  PERFORMANCE. 


141 


per  square  foot  of  heating  surface  by  Fig.  81.  The  first  diagram 
(Fig.  80)  represents  the  effect  of  changes  in  the  draft  condition  on 
combustion,  and  the  second  (Fig.  81)  upon  the  evaporative  power  of 
the  boiler.  In  both  diagrams,  for  reasons  already  in  part  explained,, 
the  points  representing  individual  tests  fall  irregularly.  An  approxi- 
mation to  the  mean  curve,  representing  draft  and  rate  of  combus- 
tion, is  shown  by  the  straight  line  (Fig.  80)  which  is  represented  by 
the  equation 

D  =  .037G,       . .     (3) 

in  which  D  is  the  draft  in  inches  of  water,  and  G  is  the  pounds  of 
coal  per  square  foot  of  grate  per  hour. 


10  20  30  40  50  60  70  80  90  100  110  120  130  140  150  160  170  180  190 

W.F.M.GOSS 

FIG.  80. — Pounds  of  Coal  per  Foot  of  Grate  per  Hoar,  as  Related  to  Draft  and 
Smoke-box  Temperature. 

The  smoke-box  temperature  as  affected  by  changes  in  the  rate 
of  combustion  is  shown  by  Fig.  80,  and  as  affected  by  changes  in 
the  rate  of  evaporation  by  Fig.  81.  From  these  figures  it  will  be 
seen  that  as  the  power  of  the  boiler  is  increased  the  smoke-box  tem- 
perature rises;  also  that,  as  in  the  case  of  the  draft,  the  points 
representing  individual  tests  fall  irregularly.  It  should  be  noticed,, 
however,  that  the  smoke-box  temperature  (Column  39)  is  lower 
than  it  is  usually  assumed  to  be.  It  varies  from  550  to  798  degrees, 
a  range  which,  considering  the  variation  in  the  rate  of  combustion 
(Column  40),  is  not  great.  Ideal  conditions  should  make  the  smoke- 
box  temperature  a  function  of  the  rate  of  combustion,  but  under 


142 


LOCOMOTIVE  PERFORMANCE. 


actual  conditions  the  relationship,  as  it  appears  in  Fig.  80,  is  not 
without  variation.  This  is  unquestionably  due  to  differences  in  fire 
condition,  the  efficiency  of  the  action  at  the  grate  varying  greatly 
for  different  tests.  Other  things  being  equal,  low  smoke-box  tem- 
perature should  be  expected  to  indicate  a  thin  fire. 

Smoke-box  temperatures,  plotted  with  evaporation,  are  given  in 
Pig.  81.  As  evaporation  is  more  directly  a  function  of  the  heat 
passing  the  tubes  than  of  furnace  action,  this  comparison  does  not 
necessarily  involve  inequalities  in  the  action  of  the  grate.  For  this 
reason  the  points  should  be  expected  to  fall  more  nearly  in  line,  but 
at  the  scale  chosen  for  the  diagram  it  must  be  confessed  that  the 
actual  difference  is  not  great. 


10 


1    2   34   5   67   8   9   10   11   12   13   14   15   16   17 

•W.F.M.Goss 

FIG.  81. — Pounds  of  Water  per  Foot  of  Heating  Surface  per  Hour,  as  Related  to 
Draft  and  Smoke-box  Temperature. 

52.  Evaporative  Performance  (Table  XXXIII). — If  it  is  remem- 
bered that  the  results  of  this,  as  of  other  tables,  are  arranged  in  order 
of  power  the  data  it  presents  will  have  increased  significance.  For 
example,  by  merely  scanning  its  columns,  the  change  in  evaporative 
efficiency  resulting  from  increased  power  may  be  seen.  The  table 
shows  the  actual  evaporation  per  pound  of  dry  coal  (Column  41)  to 
vary  from  6£  pounds  of  water  for  the  lightest  power  test  to  4.77  for 
the  heaviest.  Columns  42  and  43  show  respectively  the  evaporation 
from  and  at  212  degrees  Fahr.  for  each  pound  of  dry  coal,  assuming 


BOILER  PERFORMANCE. 


TABLE  XXXIII. 

EVAPORATIVE  PERFORMANCE. 

The  several  tests  represented  in  this  table  are  arranged  in  order  of  the  rate  of 
evaporation,  No.  1  representing  the  test  for  which  the  rate  is  least,  and  No.  35 
that  for  which  it  is  greatest. 


Identification 
oi  Test. 

Evaporative  Performance. 

Evapora- 
tion. 

Equivalent  Evaporation  from  and  at  212°  Fahr. 

g 

Dura- 
tion of 

Per  Pound  of  Dry 

Per  Pound  of  Com- 

3 

Test  in 

Coal. 

bustible. 

55 

Labora- 

Min- 

0) 

tory 

utes. 

Total 

Desig- 

Water 

Assuming 

Assuming 

s- 

nation. 

Divided 

Assuming 

all  Water 

Assuming 

all  Water 

by  Total 

Quality  of 

Delivered  to 

Quality  of 

Delivered  to 

03 

Coal. 

Steam  as 

have  been 

Steam  as 

have  been 

a 

shown  by 
Column  16. 

Completely 
Evaporated 

shown  by 
Column  16. 

Completely 
Evaporated 

into  Dry 

into  Dry 

Steam. 

Steam. 

i 

2 

4 

41 

42 

43 

44 

45 

i 

15-1-A 

240 

6.50 

7.83 

7.86 

8.70 

8.74 

2 

15-1  6-V 

190 

6.90 

8.31 

8.35 

9.24 

9.28 

3 

15-1-H 

180 

7.67 

9.15 

9.26 

10.17 

10.29 

4 

25-1-A 

255 

6.70 

8.05 

8.10 

8.95 

9.00 

5 

15-1-G 

180 

6.98 

8.37 

8.44 

9.31 

9.38 

6 

15-2-A 

180 

6.63 

7.95 

8.00 

8.84 

8.89 

7 

25-1-V 

240 

6.61 

7.95 

7.99 

8.84 

8.88 

8 

35-1-A 

180 

6.44 

7.74 

7.99 

8.61 

8.66 

9 

35-2-F 

180 

6.31 

7.61 

7.66 

8.45 

8.51 

10 

35-1-V 

140 

6.26 

7.54 

7.58 

8.38 

8.42 

11 

35-2-E 

180 

6.26 

7.54 

7.58 

8.38 

8.42 

12 

45-1-A 

150 

6.62 

7.96 

7.99 

8.83 

8.88 

13 

35-2-B 

170 

5.62 

6.75 

6.79 

7.50 

7.54 

14 

55-1  -A 

120 

6.00 

7.17 

7.24 

7.95 

8.04 

15 

35-1-H 

160 

5.95 

7.12 

7.20 

7.92 

8.00' 

16 

35-1-G 

170 

6.19 

7.41 

7.48 

8.24                8.31 

17 

35-U-G 

170 

6.44 

7.72  * 

7.80 

8.58 

8.66 

18 

25-2-A 

180 

5.99 

7.18 

7.23 

7.98 

8.04 

19 

55-1-V 

120 

5.83 

6.98 

7.03 

7.76 

7.81 

20 

35-2ft-H 

160 

5.98 

7.18 

7.25 

7.97 

8.05 

21 

55-1-H 

120 

6.40 

7.68 

7.75 

8.54 

8.62 

22 

55-1  -G 

120 

5.51 

6.59 

6.66 

7.33 

7.40' 

23 

15-9-A 

150 

5.69 

6.81 

6.86 

7.57 

7.63 

24 

15-9-H 

180 

5.40 

6.47 

6.53 

7.18 

7.26; 

25 

35-2-A 

180 

5.79 

6.94 

7.00 

7.72 

7.78 

26 

35-3-G 

140 

5.75 

6.87 

6.95 

7.63 

7.73 

27 

15-9-G 

160 

5.63 

6.74 

6.80 

7.49 

7.56 

28 

35-3-H 

120 

5.50 

6.59 

6.65 

7,32 

7.39 

29 

35-2-G 

160 

5.31 

6.35 

6.42 

7.06 

7.13 

30 

35-2-H 

120 

5.82 

6.95 

7.03 

7.73 

7.81 

31 

45-2-A 

140 

5.09 

6.09 

6.14 

6.77 

6.83 

32 

25-3-A 

122 

5.64 

6.76 

6.82 

7.51 

6.57 

33 

35-2-C 

120 

4.86 

5.86 

5.90 

6.52 

6.55 

34 

55-2-A 

68 

5.31 

6.34 

6.40 

7.04 

7.11 

35 

35-3-A 

120 

4.77 

5.71 

5.76 

6.36 

6.39 

I 

* 

141 


LOCOMOTIVE  PERFORMANCE. 


the  quality  of  the  steam  to  be  that  shown  by  the  calorimeter  (Column 
16),  and  assuming  all  steam  generated  to  have  been  dry  and  saturated. 
In  a  similar  manner,  Columns  44  and  45  show  the  equivalent  evapora- 
tion per  pound  of  combustible,  assuming  the  quality  of  steam  to  be 
that  shown  by  Column  16,  and  assuming  the  steam  to  be  dry  and 
saturated  respectively.  All  of  these  values  are  proportional  to  the 
evaporative  efficiency  of  the  boiler. 

Referring  to  the  equivalent  evaporation  per  pound  of  coal  as  it 
would  ordinarily  be  calculated  (Column  42),  it  will  be  seen  that 
for  the  lightest  power  test  the  evaporation  was  7.83  pounds,  and 
that  it  diminished  greatly,  but  somewhat  irregularly,  as  the  rate 
of  evaporation  increased,  until,  when  the  power  of  the  boiler  became 
maximum,  it  was  reduced  to  5.71,  a  loss  of  27  per  cent.  The  equivalent 
evaporation  per  pound  of  coal  for  the  several  tests  (Column  42)  and 
the  rate  of  evaporation,  as  represented  by  the  pounds  of  water  evapo- 
rated per  square  foot  of  heating  surface  per  hour  (Column  21),  are 


3O 


^ 


8   12 


2526 


ttr 


F*OUNDS  OF  W 


TER  EVAPOR 


FROM  AND  AT  212 


PER  SQUARE^OOT  J3F  HEATING  SURFACE  PER  HOUR 


1        2        3        4        5        6        7        8        9       10      11       12      13      14      15      16      17 

W.F.M.Goss 

TIG.  82. — Rate  of  Evaporation  and  Efficiency,  as  shown  by  Pounds  of  Water 
per  Square  Foot  of  Heating  Surface  per  Hour  and  Pounds  of  Water  per 
Pound  of  Coal. 

plotted  in  Fig.  82.  From  the  points  of  this  diagram  an  effort  has 
been  made  to  locate  a  curve  which  should  show  the  relation  of  the 
evaporative  efficiency  to  the  rate  of  evaporation.  The  method 
adopted  may  be  described  as  follows: 

The  several  points  were  separated  into  nine  groups,   those  of 


BOILER  PERFORMANCE. 


145 


each  group  representing  tests  of  nearly  the  same  power.    The  group- 
ing is  as  follows: 


1st  Group. 
Test    1 
"      2 

"  3 
"  4 
"  5 


€th  Group. 

Test  23 

"  24 

"  25 

"  26 

91  27 

"  28 


2d  Group. 
Test  6 

"     7 


7th  Group. 

Test  29 
"  30 
"  31 
"  32 
"  33 


3d  Group. 

4th  Group. 

Test     8 

Test   15 

"        9 

"      16 

"      10 

«      1? 

"      11 

<(     18 

"      12 

"      19 

"      13 

"     20 

"      14 

8th  Group. 

Test  34 

5th  Group. 

Test  21 

"     22 


9th  Group. 
Test   35 


The  centers  of  the  first  seven  groups  have  been  determined  and 
their  location  is  shown  on  the  diagram  by  solid  black  spots.  A 
straight  line  drawn  as  nearly  as  possible  through  the  points  thus 
located  is  assumed  to  show  the  relationship  sought.  There  are  but 
two  centers  of  groups  that  are  as  much  as  one  per  cent  away  from 
this  line,  and  four  touch  it  within  one-tenth  of  one  per  cent. 

Before  attempting  a  more  critical  examination  of  the  line  thus 
located,  it  may  be  well  to  inquire  why  so  many  of  the  points  repre- 
senting individual  tests,  and  shown  upon  the  diagram  by  light  circles, 
fall  at  so  great  a  distance  from  it.  The  facts  in  the  case  are  as  follows : 


11  points  or  31  per  cent,  of  the  whole  agree  with  the  curve  within  1  per  cent. 
15         "         43         "  "          "         "  "          "          "      2 

"      3- 


43 
51 

60 
69 

77 


There  is  a  wide-spread  feeling  among  motive-power  men  that 
the  character  of  the  exhaust  has  much  to  do  with  the  efficiency  of 
the  furnace  action;  that  a  heavy  exhaust  incident  to  slow  running 
will  have  a  different  effect  upon  the  fire  than  the  lighter  but  more 
rapid  action  attending  higher  speeds,  though  the  draft,  as  registered 
by  a  gauge  in  the  smoke-box,  may  read  the  same.  It  was  but  natural, 
therefore,  to  first  look  to  the  engine  conditions  for  an  explanation 
of  the  irregularities  in  the  efficiency  of  the  boiler.  The  result  of  such 
a  study  tends  to  disprove  the  commonly  accepted  theory,  and  justifies 


146  LOCOMOTIVE  PERFORMANCE. 

the  conclusion  that,  with  a  given  vacuum  in  the  smoke-box,  the  action 
of  the  boiler  is  quite  independent  of  the  manner  in  which  the  vacuum 
is  maintained,  whether  by  slow  heavy  beats  or  quicker,  lighter  pulsa- 
tions. For  example,  we  have  tests  1,  2,  3,  and  5,  for  which  differ- 
ences in  engine  conditions  were  confined  to  the  dimensions  or  the 
setting  of  the  valves.  All  were  run  at  a  speed  of  15  miles  an  hour, 
and  all  at  shortest  cut-off,  and  yet  the  results  are  widely  separated. 
In  the  second  group  are  tests  6  and  7,  which  check  each  other  closely, 
but  one  was  run  at  low  speed  under  a  liberal  cut-off  (15-2),  while 
the  other  was  at  a  higher  speed  and  shorter  cut-off  (25-1).  The 
third  group  consists  of  tests  8  (35-1-A),  9  (35-2-F),  10  (35-1-V),  11 
(35-2-E),  12  (45-1-A),  13  (35-2-B),  and  14  (55-1-A).  Of  tests 
numbered  8,  9,  10,  and  11,  all  at  35  miles  an  hour,  two  were  run  at 
short  cut-off,  and  two  at  a  more  liberal  one,  but  the  points  of  all  fall 
near  the  curve.  Of  the  fourth  group,  including  tests  15  (35-1-H), 
16  (35-1-G),  17,  (35-1&-G),  18  (25-2-A),  19  (55-1-V),  20  (35-26-H), 
tests  16,  18,  and  20,  which  differ  one  from  the  other  in  speed  and 
cut-off,  fall  most  nearly  upon  the  curve,  while  tests  15  and  16,  having 
the  same  conditions,  fall  on  the  opposite  side.  The  two  tests  of  the 
fifth  group,  21  (55-1-H)  and  22  (55-1-G),  both  at  the  same  high 
speed  and  short  cut-off,  fall  on  either  side  of  the  line  curve.  A  com- 
parison of  the  remaining  groups  gives  similar  results.  It  seems, 
therefore,  but  fair  to  conclude  that  variations  in  the  character 
of  the  exhaust-jet — such  as  result  from  changes  in  speed  or  cut-off- 
do  not  in  themselves  affect  the  efficiency  of  the  boiler. 

It  is  well  known  that  when  an  engine  is  working  under  a  light 
load,  a  skillful  fireman  can  maintain  a  very  thin  fire  over  the  whole 
grate.  Under  favorable  conditions  one  may  almost  see  the  grate- 
bars  through  the  fire.  All  portions  of  such  a  fire  are  bright,  and  there 
will  be  plenty  of  steam,  but  the  firing  must  be  frequent.  Such  a 
fire  offers  so  little  resistance  to  the  incoming  air  that  larger  volumes 
than  are  needed  for  combustion  pass  through  the  furnace  and  absorb 
a  portion  of  its  heat.  Again,  the  fire  may  be  made  so  thick  that 
it  will  not  burn  clear.  The  demand  for  steam  may  not  be  great, 
and  a  sluggish  and  smoky  fire  may  serve  to  generate  it.  But  such 
conditions  cannot  give  maximum  efficiency.  It  follows  that  some- 
where between  the  very  thin  fire  and  the  very  thick  fire  will  be  one 
of  such  thickness  as  will  result  in  maximum  efficiency.  For  all 
tests  here  reported  the  same  fireman  served.  He  was  skilled  in  his 
work,  and  every  effort  was  made  to  have  a  fire  suited  to  the  demands 


BOILER  PERFORMANCE. 


147 


made  upon  it.  But  the  locomotive  fireman  takes  his  cue  from  the 
steam-gauge  rather  than  from  the  furnace.  If  the  finger  of  the  gauge 
is  moving  upward,  or  holds  its  own,  the  fire  is  usually  assumed  to 
be  all  right;  if  it  falls,  something  must  be  done.  The  actual  condition 
of  the  fire  under  such  circumstances,  especially  in  a  test  for  which 
a  constant  speed  and  load  are  maintained,  depends  very  much  upon 
the  character  of  the  fire  at  the  start.  It  may  happen  that  two  tests, 
apparently  identical  as  to  speed,  load,  etc.,  may  be  run,  one  with 
a  thick  fire  and  the  other  with  a  comparatively  thin  fire,  and,  so  far 
as  outward  conditions  are  concerned,  the  tests  may  seem  equally 
satisfactory,  while  neither  satisfies  conditions  for  maximum  efficiency. 
With  these  facts  in  mind,  we  may  now  inquire  further  concerning 
the  variations  in  the  results  of  tests  to  which  attention  has  already 
been  directed.  Thus,  a  comparison  of  the  11  tests  that  agree  with  the 
mean  curve  (Fig.  82)  within  1  per  cent  with  the  11  tests  which  have 
the  greatest  divergence  from  it  reveals  the  fact  that  the  tests  of  the 
latter  class  are,  for  the  most  part,  those  in  which  the  firing  required 
unusual  care.  The  greater  part  of  the  tests  of  this  group  are  either 
tests  at  very  low  power,  for  which  only  a  light  fire  could  be  maintained 
without  danger  of  losing  steam  at  the  safety-valve,  or  tests  at  high 
speeds,  when  the  work  of  firing  was  hard  and  difficult.  Included  in 
this  group  also  is  one  test  under  low  boiler  pressures,  which  is  to  be 
regarded  as  a  light  power  test.  On  the  other  hand,  those  which  agree 
most  nearly  with  the  curve  are,  for  the  most  part,  tests  at  medium 
load,  which  were  easily  fired.  An  exhibit  of  these  facts  is  as  follows: 


Results  in  Agreement  with  the  Curve. 

Results  which  Diverge  from  the  Curve. 

Distance  which 
Points  are  off 
the  Curve. 

Laboratory 
Designation. 

Distance  which 
Points  are  off 
the  Curve. 

Laboratory 
Designation. 

Test 

Test 

Number. 

T3     **      IB 

Number. 

.    £j 

Per  Cent. 

8  I  •§ 

Per  Cent. 

f   -g  'C 

GQ     O     02 

GQ    O    02 

0 

6 

15-2-A 

10.6 

13 

35-2-B 

0.2 

35 

35-3-A 

9.9 

3 

15-1-H 

0.3 

11 

35-2-E 

8.5 

21 

55-1-H 

0.4 

7 

25-1-V 

7.9 

1 

15-1-A 

0.4 

10 

35-1-V 

7.4 

32 

25-3-A 

0.5 

8 

35-1-A 

7.3 

30 

35-2-H 

0.7 

23 

15-9-A 

6.5 

22 

55-1-G 

0.8 

27 

15-9-G 

6.2 

33 

35-2-C 

0.9 

20 

35-26-H 

5.8 

34 

55-2-A 

0.9 

16 

35-1-G 

5.4 

31 

45-2-A 

0.9 

2 

15-1  6-V 

-    5.3 

12 

45-1-A 

148  LOCOMOTIVE  PERFORMANCE. 

Accepting  the  experimental  results  as  reliable,  it  seems  safe  to 
conclude  that  variations  in  the  efficiency  of  the  boiler,  as  disclosed 
by  different  tests  at  the  same  power,  are  due  to  irregularities  in  the 
character  of  firing. 

53.  Power  and  Efficiency. — Referring  again  to  Fig.  82,  it  should 
be  noted  that  the  ordinates  in  this  diagram  represent  the  evaporative 
efficiency  of  the  boiler,  and  the  abscissae  the  rate  of  evaporation. 
The  manner  in  which  the  line  which  is  assumed  to  represent  the  mean 
of  these  points  was  drawn  has  already  been  described.     The  equation 
for  the  line  is 

E  =  10.08  -  .296#, (4) 

in  which  E  is  the  pounds  of  water  evaporated  from  and  at  212  degrees 
Fahr.  per  pound  of  coal,  and  H  the  pounds  evaporated  per  square 
foot  of  heating  surface  per  hour. 

This  equation  and  others  derived  from  it  are  assumed  to  represent 
the  average  performance  of  the  boiler  when  using  Indiana  block  coal. 
By  its  use  it  is  possible  to  obtain  a  coal  record  from  the  water  rate, 
no  weighing  being  made  of  the  fuel.  Defense  for  such  a  practice  is 
to  be  found  in  the  comparative  ease  with  which  the  water  record  is 
obtained,  and  in  the  fact  that  the  coal  consumption,  as  determined 
from  the  equation,  is  a  more  consistent  factor  than  can  ordinarily  be 
obtained  experimentally  from  a  few  tests.  The  form  of  the  equation 
will  doubtless  hold  for  all  boilers  of  similar  design  with  that  tested, 
but  the  constants  may  change  with  the  proportions  of  the  boiler, 
and  will  of  necessity  change  with  the  character  of  the  fuel  employed. 

54.  Efficiency  as  Affected  by  the  Quality  of  Fuel. — While  appar- 
ently somewhat  apart  from  the  present  purpose,  it  will  be  of  interest, 
in  connection  with  the  general  discussion,  to  review  certain  results 
which  have  been  obtained  from  five  different  samples  of  fuel  tested 
in  the  same  boiler,  and  which  were  reported  in  a  paper  presented  to 
the  Western  Railway  Club  at  the  December  meeting,   1898.     The 
several  samples  were  designated  as  A,  B,  C,  D,  and  E.     All  were 
bituminous   coals.     The   evaporation   obtained   from   each  of   these 
samples  is  shown  by  Fig.  83.     Line  D  on  the  diagram  very  nearly 
corresponds  with  that  given  in  Fig.  82  for  the  Indiana  block,  and  its 
equation  is  substantially  that  given  above.     The  equation  for  line  E, 
representing  the  best  coal,  may  be  taken  as 

Ei  =12.9  -  0.41F,       ....  (a) 


BOILER  PERFORMANCE.  149 

.and  for  line  C,  representing  the  poorest  coal,  as 

E2  =  9.4  -  0.24#.     .     ; (6) 

These  equations  probably  represent  the  range  of  variations  in  per- 
formance as  affected  by  different  qualities  of  fuel. 

The  rate  of  evaporation  represented  by  the  experiments  with  the 
Indiana  block,  upon  which  equation  4  is  based,  lies  between  the  limits 
of  5  and  15  pounds  of  water  per  square  foot  of  heating  surface  per 
hour,  while  the  limits  on  which  equations  a  and  b  are  based  are  but 
little  narrower.  The  equations,  then,  are  reliable  when  H  is  allowed 
a  value  which  is  not  less  than  5  nor  greater  than  15. 

In  this  connection  it  is  of  interest  to  note  that  the  lines  E,  A,  B, 
C,  D  converge,  and  it  may  be  assumed  that  if  D  and  C  were  sufficiently 
extended  they  would  meet;  that  is,  if  the  rate  of  evaporation  were 
made  sufficiently  high,  both  the  good  and  the  poor  coal  would  give 
the  same  evaporation.  The  point  where  this  would  happen  can  be 
determined  from  equations  a  and  6,  by  making  E\  equal  to  E%.  Thus, 

12.9  -  QAIH  =  9.4  -  0.24# 
and 

H  =  20.  approximately. 

That  is,  accepting  for  the  moment  this  equation  as  true  for  all  values 
of  H,  they  show  that  when  the  boiler  is  forced  to  evaporate  20  pounds 
of  water  per  square  foot  of  heating  surface  per  hour,  the  poorer  coal 
will  evaporate  as  much  water  per  pound  as  the  better.  It  is  evident 
that  the  equations  are  not  to  be  relied  upon  for  conditions  so  widely 
separated  from  those  covered  by  the  experiments,  and  it  is  equally 
evident  that  the  boiler  could  not  easily  be  forced  to  so  high  a  rate 
of  evaporation.  The  general  conclusion  to  be  deduced  is,  however, 
perfectly  logical.  The  higher  the  power  to  which  a  boiler  is  forced, 
the  smaller  is  the  fraction  of  the  total  heat  developed  which  can  be 
absorbed  by  the  heating  surface.  If  forced  to  very  high  power,  the 
amount  of  heat  utilized  out  of  all  that  is  available  becomes  so  small 
tnat  slight  variations  in  the  amount  available  do  not  measurably 
affect  the  amount  utilized. 

If  carried  to  extreme  limits,  it  will  doubtless  appear  that  the  line 
of  Fig.  82,  represented  by  equation  4,  is  in  fact  not  straight,  though, 
within  limits  which  are  sufficiently  broad  to  cover  all  practical  cases, 


150 


LOCOMOTIVE  PERFORMANCE. 


it  may  probably  be  so  considered.     The  form  of  this  and  of  other 
similar  lines  is  the  subject  of  discussion  in  a  preceding  paragraph. 

55.  Derived  Relations. — The  relation  between  the  rate  of  evapora- 
tion and  the  rate  of  combustion  for  the  thirty-five  tests  under  dis- 
cussion is  shown  by  Fig.  84.  The  points  in  this  figure  are  located 
from  experimental  data,  but  the  curve  which  is  assumed  to  rep- 


OLENT 
ATION 


1  2  3  4  5  6  7  8  9  10  11  12  13 

EQUIVALENT  EVAPORATION  PER  SCUARE  FOOT  OF  HEATING  SURFACE  PER  HOUR  . 

FIG.  83. — Rate  of  Evaporation  and  Efficiency  for  Five  Different  Samples  of 

Bituminous  Coal. 

resent    their    mean    value    was   plotted   from   an  equation  derived 
from  equation  4.     Thus  equation  4,  as  already  given,  is 


E  =  10.08  -.296#. 


(4) 


We  may  let  W  =  total  pounds  of  water  evaporated,  from  and  at  212 
degrees  Fahr.  per  hour,  and 

C  =  total  pounds  of  coal  fired  per  hour; 

We  may  note  also  that  1,214.4  =  square  feet  of  heating  surface  in  the 
experimental  boiler.     Then 

-E,    and    ff- 


BOILER  PERFORMANCE.  151 

or 

5- =  10.08-0.29677 


and 

W 


10.08  -0.000244TF 


(5) 


It  is  from  this  equation  that  the  curve  (Fig.  84)  was  plotted.  It 
will  be  seen  that,  while  the  curve  is  derived  quite  independently 
of  the  points,  the  two  systems  agree  closely. 

The  relation  between  water  evaporated  per  pound  of  coal  and 
pounds  of  coal  consumed  per  square  foot  of  grate  per  hour  is  shown  by 
Fig.  85. 

This  curve,  in  common  with  tne  one  preceding,  is  plotted  from 
its  equation,  which  was  obtained  as  follows: 

Having  #  =  10.08  -.296/7,      .......     (4) 

let  G  =  pounds  of  coal  per  square  foot  of  grate  per  hour.  Note  that 
17.25  =  square  feet  of  grate  surface  for  the  experimental  boiler.  It 
has  already  been  shown  that 


or 


but 


W  W 

1L+.  000244—  C=  10.08; 

c  Lf 


W     „ 

zrf* 


therefore 

#+0.000244#C  =  10,08, 
and 

10.08 
~1+0.000244<T 


152 
But 

and  therefore 


LOCOMOTIVE  PERFORMANCE. 

C  =  17.25G, 
10.08 


.00421G' 


(6) 


The  agreement  between  the  curve  plotted  from  this  equation 
and  the  experimental  points  is  as  close  in  this  case  (Fig.  85)  as  in 
those  previously  discussed.  Other  relationships  may  be  estab- 
lished by  aid  of  those  already  given.  Perhaps  the  most  interesting 
is  that  of  draft  (D)  to  total  weight  of  water  evaporated  per  hour 
(W),  which  takes  the  form  of 


D 


.00214TF 


10.08  -. 000244 JF 


(7) 


Before  leaving  this  phase  of  the  subject,  it  is  of  interest  to  note 
that  the  plotted  curves  representing  the  derived  equations  (Figs.  84 


20000 


18000 


16000 


14000 


12000 


10000 


8000 


6000 


4000 


2000 


800 


1200 


1600 


2000 


2400 


2800 


3200 


400 

*  W.F.M.GOSS 

FIG.  84. — Combustion  and  Evaporation,  as  shown  by  Total  Pounds  of  Coal  per 
Hour  and  Total  Pounds  of  Water  per  Hour. 

and  85)  are  based  upon  the  equation  of  a  straight  line.  This  straight 
line  (Fig.  82)  is  believed  to  fairly  represent  the  experimental  points 
for  which  it  stands,  and  it  follows  that  the  curves  of  Figs  84  and  85 
represent,  with  an  equal  degree  of  accuracy,  the  experimental  points 


BOILER  PERFORMANCE. 


153 


in  the  midst  of  which  they  are  drawn.  If,  however,  the  experimental 
points  represented  by  Fig.  85  had  been  accepted  as  a  starting-point 
for  the  several  curves,  a  straight  line  might  have  been  drawn  through 
them  without  difficulty.  Had  this  been  done  and  the  relation  repre- 
sented by  Fig.  82  been  mathematically  derived  from  it,  the  line  of 
Fig.  82  would  have  been  a  curve.  From  these  considerations,  and 
from  those  previously  presented  concerning  the  convergence  of  the 
several  lines  representing  different  samples  of  coal,  it  is  evident  that 
none  of  the  relationships  discussed  are  perfectly  represented  by  a 
straight  line.  But  with  nothing  but  the  experimental  point  as  a  basis, 


10  20  80  40  50  60  70  80  90  100  110  120  130  140  150  160  170  180  190  200 

W.E.M.GOSS 

i<  IG.  85. — Rate  of  Combustion  and  Efficiency,  as  shown  by  Pounds  of  Coal  per 
Square  Foot  of  Grate  per  Hour  and  Pounds  of  Water  per  Pound  of  Coal. 

it  appears  difficult  to  locate  a  line  which  will  better  represent  them 
than  the  straight  line  of  Fig.  82,  and  as  before  noted,  within  the 
limits  for  which  it  applies,  such  a  line  cannot  be  much  in  error. 

56.  Conclusions. — 1.  The  steam  delivered  by  the  boiler  tested 
under  constant  conditions  of  running,  as  shown  by  a  calorimeter 
attached  to  the  dome,  is  at  all  times  nearly  dry,  the  entrained  moisture 
rarely  equaling  1 .5  per  cent,  and  being  generally  much  less  than  this. 
While  the  relationship  cannot  be  perfectly  defined,  it  appears  that  the 
entrained  moisture  increases  slightly  as  the  rate  of  evaporation  is 
increased. 

2.  The  maximum  power  at  which  the  boiler  was  worked  with 
Brazil  block  coal  was  such  as  gave  30  boiler  horse-power  for  each 
square  foot  of  grate,  and  .427  horse-power  for  each  square  foot 
of  heating  surface.  Experiments  with  other  fuels  indicate  that 


154  LOCOMOTIVE  PERFORMANCE. 

these  values  may  be  increased  by  the  use  of  a  better  coal  by  about 
15  .per  cent,  giving  maximum  values,  which,  in  round  numbers, 
are  35  horse-power  per  square  foot  of  grate  and  .5  horse-power  per 
square  foot  of  heating  surface.  For  the  type  of  boiler  experimented 
upon,  and  under  conditions  of  constant  running,  these  values  may 
be  accepted  as  near  the  maximum. 

3.  The  maximum  rate  of  combustion  reached  was  182  pounds  of 
coal  per  square  foot  of  grate  per  hour,  which  is  equivalent  to  2.6 
pounds  per  square  foot  of  heating  surface. 

4.  The  maximum  draft  for  any  test  was  that  for  which  the  average 
value  was  7.5  inches.     If  D  is  the  reduction  of  pressure  in  the  smoke- 
box  measured  in  inches  of  water,  and  G  the  pounds  of  coal  burned 
per  square  foot  of  grate  per  hour,  then 


Also,  if  W  be  the  total  weight  of  water  evaporated  per  hour,  the 
draft  necessary  to  produce  a  given  evaporation  is  represented  by  the 
equation 

.00214TF 
10.08  -.000244TT 

These  equations  apply  to  the  boiler  tested  when  using  Indiana  block 
coal. 

5.  Smoke-box  temperature  ranges  from  550  to  800  degrees  Fahr., 
values   which   are   lower   than   those   which   are  often  assumed  to 
prevail. 

6.  The  evaporative  efficiency  of  the  boiler  as  affected  by  different 
rates  of  evaporation  is  expressed  by  the  equation 

#  =  10.08  -.296#, 

in  which  E  is  the  pounds  of  water  evaporated  from  and  at  212  degrees 
Fahr.  per  pound  of  coal,  and  H  the  pounds  of  water  evaporated  from 
and  at  212  degrees  Fahr.  per  square  foot  of  heating  surface  per  hour; 
this  for  the  boiler  tested  using  Indiana  block  coal,  and  for  values 
of  H  of  not  less  than  5  nor  greater  than  15.  With  different  coals 
the  constants  will  vary,  results  which  are  near  the  minimum  being 
expressed  by 


BOILER  PERFORMANCE.  155 

and  results  near  the  maximum  by 


These  equations  may  be  accepted  as  of  rather  general  application, 
representing  approximately  the  performance  of  any  locomotive  boiler. 

7.  The  evaporative  efficiency  of  the  boiler  as  affected  by  different 
rates  of  combustion  is  expressed  by  the  equation 

10.08 


1  +  .00421G' 

in  which  E,  as  before,  is  the  pounds  of  water  evaporated  from  and 
at  212  degrees  Fahr.  per  pound  of  coal,  and  G  the  pounds  of  coal 
burned  per  square  foot  of  grate  per  hour;  this  for  the  boiler  tested 
using  Indiana  block  coal. 

8.  The  relation  of  coal  burned  to  water  evaporated  is  expressed  by 
the  equation 

W 
10.08 -.000244  IT 

in  which  C  is  the  total  pounds  of  coal  burned  per  hour,  and  W  the 
total  pounds  of  water  evaporated  from  and  at  212  degrees  Fahr.  per 
hour;  this  for  the  boiler  tested  using  Indiana  block  coal. 

9.  The  condition  of  running  the  engines,  whether  with  long  or 
short  cut-off,  or  at  high  or  low  speed,  does  not  appear  to  affect  the 
efficiency  of  the  boiler  of  a  locomotive,  except  in  so  far  as  it  affects 
the  average  value  of  the  draft. 

10.  The  efficiency  of  the  boiler  of  a  locomotive,  as  disclosed  by 
two  different  tests,  for  which  all  conditions  of  running  are  the  same, 
may  vary  considerably,  due  doubtless  to  inequalities  in  firing. 


CHAPTER   VII. 

HIGH  RATES   OF  COMBUSTION  AND  BOILER  EFFICIENCY.* 

57.  General  Statement. — The  fact  has  already  been  established 
that,  within  limits  denned  by  practice,  the  boiler  of  any  given  locomo- 
tive is  most  efficient  when  worked  at  its  lowest  power  (Chapter  VI.). 
The  power  of  such  a  boiler  depends  upon  the  rate  at  which  coal  is 
fed  to  the  furnace,  but  the  return,  in  water  evaporated  for  each  pound 
of  coal  burned,  is  reduced  as  the  rate  of  combustion  is  increased. 

It  has  been  found  that  for  any  given  boiler  there  is  a  definite 
relationship  between  the  evaporation  per  pound  of  coal  and  the 
weight  of  coal  fired  per  hour,  and  for  the  boiler  of  the  Purdue  loco- 
motive this  relationship  has  been  determined.  (See  equation  6 
and  Fig.  85,  Chapter  VI.)  The  facts  show  that  when  coal  is  burned 
at  the  rate  of  50  pounds  per  square  foot  of  grate  per  hour,  8.3  pounds 
of  water  are  evaporated  for  each  pound  of  coal;  while  if  the  rate  of 
combustion  is  increased  to  180  pounds  per  foot  of  grate,  the  evapora- 
tion falls  to  5.7  pounds — a  loss  in  water  evaporated  per  pound 
of  coal  of  about  30  per  cent.  This  loss  may  be  due  to  a  failure  of 
the  heating  surfaces  to  absorb  properly  the  increased  volume  of  heat 
passing  over  them,  or  to  the  imperfect  combustion  of  the  fuel  upon 
the  grate,  or  it  may  be  due  to  a  combination  of  these  causes. 

That  a  portion  of  the  loss  occurs  along  the  heating  surfaces  hardly 
admits  of  question,  since  it  is  well  known  that  any  increase  in  the 
rate  of  combustion  results  in  a  rise  in  the  temperature  of  the  smoke- 
box  gases;  but  whether,  under  ordinary  conditions,  any  considerable 
portion  of  the  loss  accompanying  increased  rates  of  power  is  due  to 

*  The  experiments  discussed  in  this  chapter  were  presented  in  a  paper  before 
the  New  York  Railway  Club  at  a  meeting  held  in  September,  1896,  entitled  "Effects 
of  High  Rates  of  Combustion  upon  the  Efficiency  of  Locomotive  Boilers."  The 
experimental  facts  which  are  here  given  are  unchanged,  but  the  discussion  of  them 
is  somewhat  altered  to  include  facts  of  more  recent  development,  and  the  conclusions 
are  considerably  modified. 

156 


HIGH  RATES  OF  COMBUSTION  AND  BOILER  EFFICIENCY.  157 

imperfect  combustion  had  not  been  demonstrated  previous  to  the 
publication  of  the  results  herein  discussed,  and  it  is  this  question 
especially  that  the  present  chapter  attempts  to  treat. 

It  will  be  seen  that  a  separation  of  the  losses  which  may  occur 
at  the  grate  from  those  which  take  place  along  the  heating  surface 
could  not  be  accomplished  by  boiler-tests  alone,  because  the  results 
of  such  tests  give  the  combined  effect  of  both  these  losses.  There 
are  two  variables  involved,  and  in  order  that  either  may  be  determined 
one  must  be  given  a  constant  value.  In  the  tests  described,  action 
along  the  heating  surface  was  maintained  constant,  while  conditions 
at  the  grate  were  varied. 

Tests  were  outlined  in  which  the  total  weight  of  fuel  fired  was  to 
be  constant  throughout  the  series,  while  the  rate  of  combustion  was 
to  be  made  different  for  each  test  by  changing  the  area  of  the  grate. 
It  is  evident  that  if  the  action  at  the  grate  were  equally  efficient 
during  the  several  tests — that  is,  for  different  rates  of  combustion — 
this  provision  would  cause  the  same  amount  of  heat  to  pass  over  the 
heating  surfaces  of  the  boiler,  and  hence  would  produce  the  same 
evaporation  and  the  same  smoke-box  temperature.  If,  on  the  other 
hand,  the  combustion  should  prove  less  efficient  for  any  one  test  than 
for  others,  a  smaller  quantity  of  heat  would  sweep  the  heating  surface, 
less  water  would  be  evaporated,  and  the  smoke-box  temperature 
would  probably  be  lower. 

The  outline  provided  for  all  observations  usual  in  boiler-testing, 
and,  in  addition  to  these,  for  a  determination  of  the  weight  of  fuel 
lost  in  the  form  of  sparks,  and  for  chemical  analyses  of  the  fuel  used, 
of  the  sparks  caught,  and  of  the  smoke-box  gases. 

58.  The  Tests  and  the  Results. — The  first  test  was  run  with  the 
locomotive  under  normal  conditions.  The  whole  grate  was  covered 
with  fuel,  the  throttle  was  fully  open,  the  cut-off  approximately  6^ 
inches,  and  the  load  such  as  to  make  the  speed  25  miles  per  hour.. 
These  conditions  gave  a  rate  of  combustion  of  61  pounds  of  coal  per 
square  foot  of  grate  per  hour. 

In  preparation  for  the  second  test,  one-quarter  of  the  grate  was 
made  non-effective,  or  "deadened,"  by  a  covering  of  fire-brick  (Fig. 
86) .  The  exhaust- tip  was  reduced,  so  that  while  the  engine  was 
running  as  before  and  using  approximately  the  same  amount  of  steam, 
the  same  total  weight  of  fuel  could  be  burned  on  the  reduced  grate 
as  in  the  first  test  had  been  burned  on  the  whole  grate.  Trial  tests 
were  run,  until  it  was  known  that  the  changes  made  would  permit  the 


158 


LOCOMOTIVE  PERFORMANCE. 


desired    conditions  to  be  maintained.      The  rate  of  combustion  in 
this  test  was  84  pounds  per  square  foot  of  grate  area. 

In  preparation  for  the  third  test,  the  grate  surface  was  reduced 


a 
-1WS^» 

•q 

r-                -  MM    - 

EFFECTIVE  GRATE 
54^x34 

^ 

• 

GRATE 

FIG.  86. — Test  2. 

to  half  its  original  area  (Fig.  87),  and  the  rate  of  combustion  was 
increased  to  124  pounds  per  square  foot  of  grate  area;   and   during 


~~ 

_17%-_4  37-  . 

-17*^ 

IHPifP    EFFECTIVE  GRATE 
37x34 

•<    ^ 

I 

GRATE 

• 

FIG.  87.— Test  3. 


the  fourth  test  only  one-quarter  of  the  original  grate  was  used  (Fig. 
88) ,  the  combustion  in  this  case  rising  to  241  pounds  per  square  foot 
of  grate  surface.  .  : 


FIG.  88.— Test  4. 

It  should  be  evident,  from  what  precedes,  that  the  prescribed 
conditions  were  designed  to  make  each  test  a  duplicate  of  every  other 
test,  excepting  in  the  matter  of  grate  area,  this  being  the  one  variable 
for  the  series. 


HIGH  RATES  OF  COMBIT&&&N  AN&  BOILER  EFFICIENCY.   159 


The  coal  used  in  the  several  tests  was  of  uniform  quality,  the 
chemical  analyses  showing  no  greater  variation  than  might  occur 
in  different  samples  from  a  single  shipment.  The  maximum  weight 
of  coal  fired  per  hour  in  any  test  was  1,087  and  the  minimum  was 
1,038,  a  difference  of  less  than  50  pounds  in  more  than  a  thousand, 
while  the  variation  during  three  of  the  four  tests  does  not  exceed 
1.2  per  cent  of  the  weight  fired.  All  firing  was  done  by  one  man, 
the  attendants  engaged  in  taking  the  more  important  observations 
were  the  same  for  all  tests,  and  all  external  conditions  affecting  the 
action  of  the  boiler  were  uniform  throughout  the  series. 

Table  XXXIV  contains  the  complete  records  of  the  tests. 

59.  Grate  Losses. — Since  in  the  series  under  consideration,  the 
volume  of  heat  sweeping  the  heating  surface  was  the  same  for  all 
tests,  it  is  reasonable  to  conclude  that  any  loss  in  evaporative  effi- 
ciency attending  increased  rates  of  combustion  is  due  to  the  action 
which  goes  on  at  the  grate.  The  extent  of  such  loss  appears  in  Table 
XXXV,  Item  3  of  which  gives  the  evaporation  per  pound  of  coal 
for  each  test,  and  Item  4  the  loss  in  evaporation  in  terms  of  that  of 
Test  1.  The  results  show  that  with  each  increase  in  the  rate  of 
combustion,  the  evaporative  efficiency  diminishes.  When  the  com- 
bustion is  forced  to  241  pounds  of  coal  per  foot  of  grate  surface  per 
hour,  the  loss  in  the  evaporation  per  pound  of  coal,  in  terms  of  that 
which  was  obtained  when  the  rate  of  combustion  was  61  pounds,  is 
19  per  cent.  This  loss  at  the  grate  may  have  its  source  in  any  one 
or  all  of  several  causes:  (1)  A  portion  of  the  coal  delivered  to  the 
fire-box  may  be  dissipated  in  the  form  of  sparks;  (2)  the  oxidation 
of  the  combustible  gases  may  be  incomplete;  (3)  the  fire-box  may  be 
cooled  by  excess  air. 

The  probable  extent  of  losses  resulting  from  these  causes  will  next 
be  considered. 

60.  Spark  Losses  as  a  Factor  Affecting  Grate  Losses. — The  data 
show  that  a  large  portion  of  the  loss  which  occurs  at  the  grate  when 
the  rate  of  combustion  is  increased,  is  due  to  losses  of  sparks.  The 
facts  involved  are  well  shown  by  Table  XXXVI.  A  comparison  of 
values  under  Item  6  of  this  table  will  show  the  rate  of  increase  in  the 
spark  losses  with  increased  rate  of  combustion.  For  example,  when 
the  rate  of  combustion  is  61  pounds,  4.3  per  cent  of  the  coal  fired  is 
accounted  for  as  sparks,  whereas  when  the  rate  of  combustion  is 
increased  to  241  pounds,  15  per  cent  of  the  coal  fired  is  thus  lost. 
The  rate  of  increase  in  spark  production  may  best  be  seen  by  assuming 


160 


LOCOMOTIVE  PERFORMANCE. 

TABLE  XXXIV. 
OBSERVED  AND  CALCULATED  DATA. 


1    Test  number.  . 

1 

2 

3 

4 

2.  Month  and  day  (1896)  

Feb.  8 

Feb.  11 

Feb.  15 

Feb.  22 

3.  Duration  of  test,  hours  

6 

6 

6 

6 

4.  Approximate    portion    of   whole 

grate  used  

Full 

Three- 

Half 

One-  fourth 

fourths 

5.  Exact   area    of   effective   grate, 

square  feet  

17.50 

13.01 

8.74 

4.31 

6.  Barometric  pressure,  pounds.  .  .  . 

14.41 

14.43 

14.34 

14.47 

Analysis  of  Coal.* 

7.  Per  cent  fixed  carbon  

49.65 

51.84 

51.09 

51.59 

8.  Per  cent  volatile  matter  

40.29 

39.00 

38.93 

38.87 

9.  Per  cent  combined  moisture  

3.15 

3.62 

2.35 

3.44 

10    Per  cent  ash.  . 

6.91 

5.54 

7.63 

6.10 

Coal  (Brazil  Block). 

11.  Pounds  fired  

6522 

6628 

6716 

6328 

12.  Weight  of  water  in  each  pound 

of  coal  fired  

0.012 

0.016 

0.  030 

0.012 

13.  Pounds  of  dry  coal  for  test  

6443 

6522 

6514 

6227 

14.  Pounds  of  dry  coal  per  hour  

1074 

1087 

1086 

1038 

15.  Pounds  of  dry  coal  per  hour  per 

square  foot  of  grate 

61.4 

83.5 

124.2 

240.8 

16.  Pounds  of  combustible  for  test.  . 

5792 

5921 

5856 

5635 

17.  Percentage    of   fixed    carbon   in 

coal,  dry  and  free  from  ash  .  .  . 

56 

57 

57 

57 

18.  Approximate  number  of  B.T.U. 

per  pound  of  combustible  

13800 

14040 

14040 

14040 

19.  Approximate  number  of  B.T.U. 

per  pound  of  dry  coal  

13000 

13000 

13000 

13000 

20.  Theoretical  evaporation  from  and 

at  212°  per  pound  of  dry  coal. 

13.46 

13.46 

13.46 

13.46 

Ash. 

21.  Pounds  of  dry  ash  in  ash-pan 

for  test  

446 

396 

297 

164 

22.  Pounds  of  ash  in  coal  fired  as 

shown  by  analysis  of  coal  

445 

361 

497 

380 

23.  Pounds  of  ash  by  analysis,  minus 

pounds  found  in  ash-pan  

-1 

-35 

200 

216 

Analysis  of  Sparks.* 

24.  Per  cent  of  fixed  carbon  

61.74 

64.88 

71.32 

76.44 

25.  Per  cent  volatile  matter  

4.36 

4.16 

3.45 

3.29 

26.  Per  cent  combined  moisture  

1.82 

1.82 

1.66 

1.86 

27.  Per  cent  ash  

32.08 

29.14 

23.57 

18.41 

Sparks. 

28.  Pounds  caught  in  front  end  dur- 

ing test.  .  .                      

75 

213 

494 

566 

29.  Pounds  passing  out  of  stack  for 

test  

294 

358 

278 

492 

HIGH  RATES  OF  COMBUSTION  AND  BOILER  EFFICIENCY.  161 
OBSERVED  AND  CALCULATED  DATA— (Continued). 


Test  number.  . 

1 

2 

3 

4 

30.  Total  pounds  of  sparks  for  test.  . 
31.   Pounds  of  sparks  per  square  foot 
of  grate  per  hour  
32.  Pounds  of  combustible  in  sparks 
for  test  .... 

369 
3.5 
242 

571 
7.3 
395 

772 
14.7 
576 

1058 
41.0 

837 

33.  Percentage    of   fixed    carbon   in 
sparks  dry  and  free  from  ash  .  . 
34.  Approximate  B.T.U.  per  pound 
of  sparks  
35.  Pounds    of    coal    equivalent    in 
heating  value  to  one  pound  of 
sparks.  .                                   ... 

94 
9870 

0.75 

94 
10360 

0.80 

95 
11200 

0.86 

96 
11880 

0.91 

36.  Pounds    of    coal    equivalent    in 
heating  value  to  total  weight 
of  sparks  for  test  

Analysis  of  Smoke-box  Gases.* 
37    Per  cent  carbon  dioxide.  .  .  . 

277 
5  45 

457 
6.25 

664 
4.80 

963 
1.80 

38.  Per  cent  heavy  hydrocarbons.  .  .  . 
39.  Per  cent  oxygen  

0.50 
12.15 

0.40 
11.80 

0.40 
14.60 

0.50 
18.70 

40    Per  cent  carbon  monoxide.  . 

0.00 

0.00 

0  00 

0  55 

41.  Per  cent  nitrogen  

Other  Smoke-box  Data. 
42.  Diameter  of  double  exhaust-  tip, 
inches.  .  .  . 

81.90 
3 

81.55 
2.75 

80.20 
2  35 

78.45 
1.75 

43.  Draft  in  inches  of  water  
44.  Temperature  of  smoke-box,deg.F. 

Water  and  Steam. 
45.  Pounds    of    water    delivered    to 
boiler.  ...                       

2.2 

647 

44756 

2.5 

629 

43081 

3.3 
610 

40710 

5.6 

500 

34770 

46.  Temperature  of  feed,  deg.  F  
47.   Boiler  pressure,  by  gauge  
48.  Quality  of  steam  in  dome  

54.0 
129.4 

0  982 

53.0 
127.2 

0  981 

53.0 
127.2 

0.984 

52.7 
129.1 
0.983 

Evaporation. 
49.  Pounds  of  water  evaporated  per 
pound  of  dry  coal  
50.  Equivalent  evaporation  from  and 
at  212°  F. 

6.94 

8.26 

6.60 

7.87 

6.30 
7.52 

5.58 
6.67 

Horse-  power. 
51.  Horse-power  of  boiler  
52.  Horse-power  per  square  foot  of 
grate  

257 
15 

248 
19 

226 
26 

201 
47 

Approximate  Efficiency.^ 
53.  Ratio  of  heat  developed  in  the 
furnace  to  heat  absorbed  by 
water  

0.61 

0.59 

0,56 

0.50 

*  All  chemical  analyses  were  made,  under  the  direction  of  Professor  W.  E.  Stone  bv 
Charles  D.  Test,  A.C. 

t  The  efficiency  is  approximate  only,  since  the  heating  value  of  the  coal  is  only  approxi- 
mately known.  But  as  the  same  coal  was  used  for  all  tests,  there  can  be  no  error  in  using 
his  factors  for  purposes  of  comparison  within  the  limits  of  the  present  series  of  tests. 


162 


LOCOMOTIVE  PERFORMANCE. 


the  spark  loss  for  Test  No.  1  to  be  zero,  the  values  for  all  tests  then 
becoming  4.3  per  cent  less  than  those  given  in  Item  6.  The  increase 
on  this  basis  is  shown  by  Item  7. 

TABLE  XXXV. 


1.  Number  of  test  

1 

2 

3 

4 

2.  Rate  of  combustion,  pounds    of 

coal  per  foot  of  grate  surface 

per  hour  

61 

84 

124 

241 

3.  Equivalent  evaporation  from  and 

at  212°  F.  per  pound  of  coal, 

pounds  

8.26 

7.87 

7.52 

6.67 

4.  Loss  of  evaporation  in  terms  of 

the  evaporation  for  Test  No.  1, 

per  cent. 

0.0 

4.7 

9.0 

19.2 

By  comparing  Item  4,  of  Table  XXXV.,  with  Item  7,  of  Table 
XXXVI.,  the  proportion  of  the  whole  loss  occurring  at  the  grate, 
which  is  accounted  for  as  sparks,  may  be  made  to  appear.  Such  a 
comparison  is  presented  as  Table  XXXVII.  In  this  table,  Item  3 
presents  the  loss  by  evaporative  efficiency  as  the  rate  of  combustion 
is  increased,  Item  4  the  fuel  loss  due  to  sparks,  and  Item  5  the  differ- 
ence. The  significance  of  this  comparison  will  appear  when  it  is 
remembered  that  if  spark  production  accounted  for  all  of  the  loss 
which  has  been  shown  to  occur  at  the  grate,  the  values  of  Item  4 
would  be  equal  to  those  of  Item  3.  The  difference,  as  disclosed  by 
Item  5,  is  therefore  the  loss  unaccounted  for  which  occurs  at  the  grate. 
It  is  relatively  very  small,  representing  only  8  per  cent  of  the  fuel 
fired  when  the  abnormally  high  rate  of  combustion  of  240  pounds 
is  maintained. 

TABLE  XXXVI. 


1    Number  of  test  

1 

2 

3 

4 

2.  Rate   of  combustion,   pounds   of 
coal  per  foot  of  grate  surface 
per  hour.  .  .                           .... 

61 

84 

124 

241 

3.  Total  pounds  of  coal  per  hour.  .  .  . 
4.  Total  pounds  of  sparks  per  hour  .  . 
5.  Fuel  value  of  sparks,  B.T.U.  per 
pound.  . 

1,074 
61.5 

9,870 

1,078 
95.1 

10,360 

1,086 
128.6 

11,200 

1,038 
176.3 

11,880 

6.  Value  of  spark  losses  in  per  cent 
of  coal  fired  
7.  Increase  of  spark  losses  over  those 
of  Test  No.  1,  in  per  cent  of  coal 
fired.  ...                              

4.3 

0.0 

7.2 
3.9 

10.2 
5.9 

15.5 
11.2 

HIGH  RATES  OF  COMBUSTION  AND  BOILER  EFFICIENCY.  163 
TABLE  XXXVII. 


1.  Number  of  test.  

1 

2 

3 

4 

2.  Rate  of  combustion,  pounds  

61 

84 

124 

241 

3.  Loss  of  evaporation  in  terms  of 

the  evaporation  for  Test  No.  1, 

per  cent  

0.0 

4.7 

9.0 

19.2 

4.  Fuel  loss  by  sparks  in  excess  of 

those  lost  in  Test  No.    1,   per 

cent  

0.0 

3.9 

5.9 

11.2 

5.  Difference  unaccounted  for  (Item 

3-Item  4).. 

0.0 

0.8 

3.1 

8.0 

61.  Losses  Due  to  Incomplete  Combustion  and  Excess  Air. — 

The  tests  show  losses  on  these  accounts  to  be  small,  since  all  loss 
occurring  at  the  grate  not  accounted  for  as  sparks  is  that  appearing 
in  Item  5  of  Table  XXXVII.  In  service  the  rate  of  combustion 
does  not  often  exceed  125  pounds  of  coal  per  hour,  for  which  all  losses 
unaccounted  for,  which  must  include  incomplete  combustion  and 
excess  air,  do  not  exceed  3  per  cent. 

62.  Losses  Along  the  Heating  Surface. — In  the  special  tests  under 
consideration  the  heating  surfaces  were  swept  by  the  same  volume 
of  heat  throughout  the  series.     By  comparing  the  evaporation  per 
pound  of  coal  under  different  rates  of  combustion  for  these  special 
tests  with  that  evaporation  which   results  under  normal  conditions 
of  operation,  there  will  be  shown  the  extent  of  the  loss  which  under 
normal  conditions  occurs  along  the  heating  surface  when  the  rate 
of  combustion  is  increased.     The  facts  involved  by  such  a  comparison 
are  set  forth  in  Table  XXXVIII.     Item  3  of  this  table  gives  the 
evaporation  per  pound  of  coal  as  derived  from  the  series  of  special 
tests  for  which  different  rates  of  combustion  were  employed  while 
maintaining  uniform  action  along  the  heating  surface.     These  values 
show,  as  already  explained,  those  losses  only  which  occur  at  the  grate. 
Item  4  gives  the  evaporation  per  pound  of  coal  under  normal  condi- 
tions of  operation,   as  obtained  from  the  equation  deduced  from 
thirty-five   tests   as   explained   in   Chapter  VI.       A   comparison    of 
the  values    of  this  item   discloses    all    losses  which    under    normal 
conditions  occur  with  increased  rates  of  combustion;    they  include 
both  those    losses  which  appear  in  Item  3  and  also  those   which 
occur   along    the   heating   surface.     The   loss   which   under   normal 
conditions  occurs  along  the  heating  surface  when  the  rate  of  combustion 
is  increased  should,  therefore,  appear  in  the  difference  between  the 
values  of  Items  3  and  4.    This  is  given  as  Item  5.     To  make  such 


164 


LOCOMOTIVE  PERFORMANCE. 


a  comparison  effective,  however,  there  is  need  of  one  correction. 
Thus,  values  for  Test  1,  Items  3  and  4,  are  assumed  to  represent 
identical  conditions  and  should  in  fact  be  the  same.  The  difference 
of  .26  of  a  pound  is  due  to  the  fact  that  the  experimental  result  (Item 
3)  does  not  fall  quite  on  the  curve  based  upon  many  different  tests 
from  which  the  equation  underlying  Item  4  was  derived.  The  facts 
are  best  shown  by  Fig.  89,  in  which  the  dotted  line  represents  the 


20          40          60          80         100        120        140        160        180        200        220        240 
Pounds  of  Coal  per  Foot  of  Grate  per  Hour 

FIG.  89. — Evaporative  Efficiency  and  Rate  of  Combustion. 

special  tests,  and  the  curve  ab  the  standard  equation  for  the  experi- 
mental boiler.  Since  the  present  discussion  is  chiefly  concerned  in 
the  relative  slope  of  the  curves,  comparison  will  be  facilitated  if  they 
have  one  common  point.  This  can  be  accomplished  by  dropping 
the  curve  of  the  special  tests  down  to  the  position  ac,  Fig.  89,  which 
involves  a  reduction  of  the  several  values  of  Item  3  (Table  XXXVIII). 
The  corrected  differences  then  become  those  appearing  as  Item  6. 
These  values  are  comparable  with  those  of  the  last  items  of  the  three 
tables  immediately  preceding. 


HIGH  RATES  OF  COMBUSTION   AND  BOILER  EFFICIENCY.   165 
TABLE  XXXVIII. 


1.  Number  of  test  
2.  Rate  of  combustion,  pounds  of  coal 
per  foot  of  grate   surface  per 
hour.  .               .  .        

1 
62 

2 

84 

3 

124 

4 

241 

3.   Equivalent  evaporation  from  and 
at  212°  F.   per  pound  of  coal 
fired  in  special  tests  
4.  Equivalent  evaporation,  from  and 
at  212°  F.   per  pound  of  coal 
fixed,  which   would  have  been 
obtained  had  the  same  rate  of 
combustion     been     maintained 
over  the  whole  area  of  the  grate: 
10.08 

8.26 

8  00 

7.87 
7  38 

7.52 
6  63 

6.67 
5  01 

1  +  .00421C?  ' 
5.  Difference  (3-4)  

0.26 

0.49 

0.89 

1.66 

6.  Difference,  Item  5  less  .26  

0.00 

0.23 

0.63 

1.40 

40 


GO          80        100        120        140        160        180        200 
Pounds  of  Coal  per  Foot  of  Grate  per  Hour 

FIG.  90. — Losses  in  Evaporative  Efficiency. 


220 


240 


63.  Conclusions. — The  significance  of  the  results  disclosed  by 
Tables  XXXV.  to  XXXVIII.,  inclusive,  are  well  shown  by  means  of 
Fig.  90,  in  which  the  curve  ab  represents  the  normal  evaporative 


166  LOCOMOTIVE  PERFORMANCE. 

efficiency  of  the  boiler  under  different  rates  of  combustion.  The 
curve  ac  represents  the  evaporative  efficiency  under  the  special 
tests  for  which  losses  along  the  heating  surfaces  are  eliminated. 
The  curve  ad  represents  the  results  which  would  have  been  obtained 
from  the  special  tests  had  there  been  no  spark  losses,  and  the  line 
ae  represents  an  evaporative  efficiency  of  constant  value.  Under 
normal  conditions  of  operation,  the  area  bac  represents  that  portion 
of  the  loss  which  takes  place  along  the  heating  surface.  The  area 
cae  represents  that  portion  of  the  loss  which  takes  place  at  the  grate, 
of  which  loss  that  represented  by  the  area  cad  is  known  to  be  due 
to  spark  production,  while  that  represented  by  the  area  dae  remains 
unaccounted  for. 

Speaking  in  very  general  terms,  it  appears  that,  under  normal 
conditions  of  service,  about  one-half  of  the  heat  loss  which  results 
from  forcing  a  boiler  to  higher  power  takes  place  along  the  heating 
surface  and  is,  of  course,  unavoidable.  Of  the  remainder,  a  very 
considerable  portion  is  represented  by  the  spark  loss.  The  portion 
remaining  unaccounted  for  is,  within  limits  of  operation  common  to 
practice,  small. 


CHAPTER  VIII. 
THE  EFFECT  OF  THICK  FIRING  ON  BOILER    PERFORMANCE. 

64.  The  Conception  Underlying  these  Tests. — It  has  already  been 
shown  (Chapter  VI.)  that  the  efficiency  of  the  boiler  of  a  locomotive 
may  vary  between  wide  limits,  even  when  there  is  no  corresponding 
change  in  the  power  delivered.  For  example,  in  Fig.  85,  Chapter  VI.. 
che  points  representing  the  results  of  experiments  are  in  many  cases 
at  some  distance  from  the  mean  curve  upon  which  they  should  fall 
In  reviewing  the  data  it  has  appeared  that  if  the  fire  had  been  main- 
tained with  an  equal  degree  of  efficiency  in  all  of  the  thirty-five  tests 
reported,  every  point  in  Fig.  85,  Chapter  VI.,  would  have  fallen  on 
the  curve  given,  or  upon  some  other  curve  closely  approaching  that 
which  is  shown.  For  this  reason  it  has  been  assumed  that  the 
differences  in  boiler  performance  noted  are  effects  resulting  from 
changes  in  the  condition  of  the  fire,  the  extent  of  which  in  any  indi- 
vidual case  is  not  easily  detected  by  the  fireman. 

The  fireman  of  a  locomotive  is  guided  in  his  work  by  the  indications 
of  the  pressure-gauge  rather  than  by  the  general  condition  of  the  fire. 
So  long  as  the  indication  of  the  gauge  is  satisfactory  but  little  attention 
is  given  the  fire,  so  that  whenever  the  conditions  of  running  are  constant 
and  favor  easy  steaming,  the  fire  passes  through  a  cycle  of  changes 
somewhat  as  follows: 

1.  Fresh  coal  is  spread  on  the  surface  of  the  fire. 

2.  The  fresh  fuel  burns  rapidly,  the  temperature  of  the  furnace 

increases,  the  pressure  responds  to  the  increased  activity 
at  the  grate,  and  the  gauge  goes  up. 

3.  The  fire  in  due  time  reaches  a  condition  of  maximum  ef- 

ficiency, and  enters  upon  a  process  of  decline.  It  allows 
the  passage  of  much  more  air  than  is  needed  for  complete 
combustion,  but  since  the  engine  is  running  under  con- 
ditions easily  sustained,  a  fire  of  even  low  efficiency  is 

167 


168  LOCOMOTIVE  PERFORMANCE. 

sufficient  to  maintain  the  pressure,  and  the  fireman  who 
watches  the  gauge  sees  no  occasion  for  opening  the  fire-box 
door. 

4.  From  being  thin  the  fire  becomes  open  and  in  spots  even 

dead.  The  influx  of  air  through  this  open  fire  increases 
until  its  volume  is  so  far  in  excess  of  that  required  for 
combustion  that  the  efficiency  of  the  furnace  falls  to  a 
point  where  it  cannot  supply  the  steam  required  by  the 
cylinders. 

5.  The  hand  of  the  gauge  moves  downward  and   the  fireman 

adds  new  coal, which  serves  as  the  starting-point  for  another 
round  of  changes  similar  to  those  which  have  just  been 
described. 

The  extent  to  which  the  routine  defined  above  occurs  in  practice 
depends  upon  the  condition  of  running.  Probably  the  greatest  loss 
from  excess  air  occurs  when  the  conditions  of  running  favor  easy 
steaming,  though  there  is  ample  evidence  to  prove  that  this  is  not 
always  so.  In  any  case,  a  remedy  is  to  be  found  in  maintaining  the 
proper  thickness  of  fire,  or  by  checking  the  draft  on  a  fire  that  is  too 
thin  by  means  of  the  ash-pan  dampers.  Practically,  however,  the 
difference  between  a  fire  that  is  too  thin  and  one  that  is  just  thick 
enough  is  a  matter  not  easily  determined. 

65.  The  Tests  and  their  Results. — The  lack  of  harmony  in  the 
results  of  the  thirty-five  tests  already  presented  suggested  the  con- 
siderations mentioned  above,  and  the  fact  that  they  well  represent 
conditions  of  practice  emphasized  their  importance.  With  a  view  to 
demonstrating  the  losses  incident  to  normal  firing,  it  was  determined  to 
run  a  series  of  tests  at  different  powers,  under  conditions  which  would 
allow  the  continuous  maintenance  of  a  thick  fire,  the  care  of  which 
should  be  at  all  times  based  upon  furnace  action,  rather  than  upon 
steam  pressure.  It  was  thought  that  the  results  of  such  a  series  might 
serve  in  the  location  of  a  curve  similar  to  that  of  Fig.  91,  which  rep- 
resents the  average  evaporative  efficiency  as  previously  defined,  and 
that  by  avoiding  thin  fires  the  points  sought  would  be  found  above 
the  average  curve.  In  accordance  with  this  conception,  tests  were 
outlined  upon  the  following  principle: 

1.  The  force  of  the  exhaust  producing  the  draft  was  to  remain 
constant  throughout  each  test,  this  condition  to  be  secured 
by  running  the  engine  under  a  constant  speed,  load,  cut- 
off, and  throttle-opening.  The  draft  itself,  as  measured 


EFFECT  OF  THICK  FIRING  ON  BOILER  PERFORMANCE.    169 

by  the  vacuum  in  the  smoke-box  might  vary  somewhat,* 
but  the  conditions  just  specified  would  make  the  force  of 
the  exhaust-jet  practically  constant. 

2.  With  the  exhaust  action  constant,  it  was  proposed  to  main- 

tain a  heavy  fire,  and  to  make  all  the  steam  that  could 
possibly  be  generated.  If  more  was  generated  than  was 
needed  by  the  cylinders,  the  excess  was  to  be  blown  out 
at  the  safety-valve. 

3.  The  engines  of  the  locomotive  were  to  have  no  part  in  the 

results,  except  that  of  providing  a  constant  draft  action; 
hence  the  purpose  of  the  test  would  not  be  interfered  with 
by  wasting  steam  from  the  safety-valve. 

4.  The  duration  of  each  test  was  to  be  such  as  would  result 

in  the  evaporation  of  not  less  than  30,000  pounds  of 
water. 

5.  The  draft  condition  for  each  test  was  to  be  such  as  could 

easily  be  maintained,  and  so  chosen  for  the  different  tests 
that  the  rates  of  combustion  resulting  would  cover  fairly 
well  the  range  of  conditions  common  to  practice. 

It  will  be  seen  from  the  foregoing  outline  that  the  fundamental 
idea  was  to  have  the  fire  always  in  a  condition  of  maximum  efficiency; 
to  have  coal  applied  whenever  the  condition  of  the  fire  made  it  desir-* 
able,  instead  of  waiting  until  the  steam-gauge  should  prompt  the  fire- 
man, and  to  have  the  fireman  watch  the  fire-box  rather  than  the 
steam-gauge. 

The  labor  of  carrying  out  the  work  prescribed  by  such  an  outline 
was  undertaken  by  Mr.  0.  Harlan,  while  a  graduate  student  in  the 
laboratory,  and  the  brief  summary  of  results  which  is  here  presented 
has  been  abstracted  from  an  elaborate  thesis  presented  by  him. 

The  firing  was  by  Charles  Reyer,  who  alone  had  performed  this 
part  in  connection  with  the  testing-plant  for  several  years  previous 
to  the  tests.  His  instructions  were  to  keep  a  heavy  fire  and  to  burn 
all  the  coal  that  the  draft  would  handle,  the  expectation  being  that 
a  full  return  for  all  fuel  burned  would  be  found  in  the  water  evaporated. 

The  general  results  are  shown  in  Table  XXXIX. 

66.  Interpretation  of  the  Results. — Plotting  the  equivalent  evapor- 
ation with  the  curve  defining  the  normal  performance  of  the  boiler,  as 
determined  from  the  thirty-five  tests  already  discussed,  it  will  be  seen 

*    Slight    changes    in    the    condition  of  the  fire    itself   affect  the    draft  action^ 
(Chapter  XL) 


170 


LOCOMOTIVE  PERFORMANCE. 


TABLE  XXXIX. 


Number  of  test  ... 

1 

2 

3 

Month  and  day  in  1897. 

Feb.  27 

April  5 

March  6 

Duration  of  test,  minutes.  .  .                          ... 

360 

180 

170 

Barometric  pressure     . 

14.8 

14.3 

14  6 

Fuel. 

5673 

6055 

6507 

Coal  per  hour.                       

945 

2018 

2297 

Coal  per  foot  of  grate  per  hour.  . 

54 

115 

131 

Water  and  Steam. 

52.4 

55.3 

54.8 

Pressure  in  boiler 

128.8 

128.4 

127.1 

Moisture  in  steam   per  cent.                    

1.5 

1.4 

1.7 

Water  delivered  to  the  boiler.  .                

36228 

32734 

34500 

Water  evaporated  per  pound  of  coal  
Equivalent  evaporation  per  pound  of  coal  
Equivalent  evaporation  per  hour.  . 

6.39 
7.42 
7011 

5.41 
6.17 
12451 

5.30 
6.13 
14080 

10 


40 


60          80        100        120        140        160        180        200        220        240 
Pounds  Coal  per  Foot  of  Grate  per  Hour 


FIG.  91. — Evaporative  Efficiency  obtained  as  a  Result  of  Thick  Firing  as  com* 
pared  with  a  Curve  of  Normal  Efficiency. 


EFFECT  OF  THICK  FIRING  ON  BOILER  PERFORMANCE.    171 

(Fig.  91)  that  the  points  all  fall  low;  the  loss  of  evaporative  efficiency 
measured  in  the  per  cent  of  normal  efficiency  being 

for  Test  No.  1 


for  test  No.  2 

^1-617 

681  /0t 

for  test  No.  3 


The  results  are  the  reverse  of  those  which  were  expected.  They 
do  not,  however,  prove  the  non-existence  of  the  defective  conditions 
which  it  was  sought  to  overcome,  but  rather  that  an  effort  to  meet 
them  if  pursued  too  vigorously  may  lead  to  worse  conditions.  A  fire 
that  is  too  thin  is  bad,  but  the  results  of  these  special  tests  prove  that 
one  which  is  too  thick  may  be  worse. 

67.  The  Influence  of  the  Fireman.  —  The  tests  and  the  results  ob- 
tained therefrom  emphasize  the  importance  of  the  fireman  as  a  factor 
in  the  economical  operation  of  the  boiler.  As  the  work  of  the  tests 
progressed  the  fireman  was  impressed  with  the  belief  that  he  was  not 
getting  the  best  possible  results,  although  in  carrying  out  the  directions 
which  had  been  given  him  he  was  attentive  and  painstaking.  The 
results  corroborate  this  opinion,  and  it  is  probably  true  that  an  experi- 
enced fireman  can  judge  with  accuracy  when  his  fire  is  in  a  condition 
to  make  the  boiler  do  its  best,  but  the  variations  in  performance 
under  conditions  which  are  identical,  as  recorded  in  the  previous 
chapter,  are  proof  that  even  though  the  man  be  one  of  exceptional 
ability  and  skill  no  very  nice  discrimination  can  be  made. 

The  conclusions  to  be  reached  from  these  tests  may  be  summa- 
rized as  follows: 

1.  A  fire  may  be  readily  maintained  so  thick  as  to  greatly  impair 

the  efficiency  of  the  boiler,  probably  because  of  an  insuffi- 
cient supply  of  air. 

2.  Between  the  limits  of  a  very  thin  and  a  very  thick  fire, 

there  probably  is,  for  every  condition  of  draft,  a  correspond- 
ing thickness  of  fire  which  will  give  maximum  efficiency. 

3.  While  the  tests  of  the  preceding  chapter  show  striking  vari- 

ations in  boiler  performance  under  conditions  which  are 


172  LOCOMOTIVE  PERFORMANCE. 

identical,  those  now  under  discussion  emphasize  the  im- 
portance of  the  fireman's  judgment  and  skill  as  factors 
affecting  the  efficiency  of  a  locomotive  boiler. 

4.  The  results  emphasize  the  difficulty  to  be  met  in  any  attempt 

to  duplicate  results  from  tests  of  a  boiler  of  a  locomotive 
when  fired  with  coal. 

5.  The  importance  of  a   thorough  study  of  the  smoke-box 

gases  in  any  precise  analysis  of  boiler  action  is  also  made 
evident  by  the  results,  a  fact  which  at  the  time  the  tests 
were  made  had  not  been  fully  appreciated. 


CHAPTER   IX. 

SPARK  LOSSES.* 

68.  Sparks. — The  passage  over  the  heating  surface  of  a  boiler  of 
particles  of  fuel,  more  or  less  consumed,  in  the  form  of  sparks  or 
cinders,  is"  by  no  means  an  inconsiderable  source  of  loss.  Experi- 
ments for  the  purpose  of  determining  the  extent  of  this  loss  were  first 
undertaken  in  connection  with  the  tests  for  efficiency  at  high  rates 
of  combustion  recorded  in  Chapter  VII.,  and  were  afterward  continued 
as  a  feature  of  the  regular  efficiency  tests,  the  results  from  certain 
of  which  are  herewith  presented. 

Solid  particles  from  the  fire  either  lodge  in  the  front  end  or  pass 
out  from  the  top  of  the  stack.  Those  which  lodge  in  the  front  end 
are  sometimes  called  front-end  cinders,  those  which  pass  from  the 
stack  being  sparks;  but  in  this  discussion  the  term  sparks  will  be 
understood  to  include  all  solid  matter  passing  the  tubes.  It  will  appear 
hereafter  that  the  composition  of  the  cinders  and  sparks  may  vary 
from  slightly  burnt  coal  to  ash.  In  determining  the  extent  of  the 
fuel  loss,  resulting  from  the  flight  of  solid  particles  from  the  fire,  it  is 
not  difficult  to  ascertain  the  weight  of  cinders  which  lodge  in  the  front 
end,  for  they  may  be  readily  collected  at  the  end  of  a  test.  The  deter- 
mination of  the  weight  of  sparks  passing  out  of  the  stack  is  a  matter 
of  more  difficulty.  In  the  experiments  in  question,  this  was  accom- 
plished by  intercepting  portions  of  the  stream  issuing  from  the  stack, 
and  by  collecting  the  sparks  entrained  therein.  From  samples  thus 
obtained,  the  weight  of  sparks  in  the  entire  stream  was  estimated. 
For  this  work  certain  special  apparatus  was  designed  and  constructed 
which  has  since  been  known  as  a  spark-trap. 

*  See  also  "Locomotive  Sparks,"  published  by  John  Wiley  &  Sons,  New  York 
City,  for  a  discussion  of  the  distribution  of  sparks  on  either  side  of  the  track,  and  the 
chance  that  fires  may  start  therefrom. 

173 


174  LOCOMOTIVE  PERFORMANCE. 

69.  The  Spark- trap  (Fig.  92)  consisted  of  an  inverted  U  tube 
of  galvanized  iron,  securely  fastened  to  a  movable  frame,  by  means 
of  which  the  tip,  which  constituted  one  extremity  of  the  tube,  could  be 
projected  across  the  top  of  the  locomotive  smoke-stack.  The  outer 
end  of  the  tube  could  thus  be  made  to  intercept  a  portion  of  the 
stream  issuing  from  the  stack,  and  the  continuous  action  of  this  stream 
was  sufficient  to  drive  the  intercepted  portion  through  the  tube  and 
out  at  the  other  end.  The  gases  passing  the  tube  bore  the  sparks  on 
their  current,  and  they  were  collected  in  a  suitable  galvanized  iron 
receptacle  set  to  entrap  them.  The  connection  between  the  tube  and 


GALVANIZED  IRON 
TUBE  FASTENED 
TO  SLIDING  FRAME 


FIG.  92.— Spark-trap. 

the  receptacle  was  screened  by  brass  milk-strainer  netting.  Reference- 
marks  upon  the  sliding  and  the  fixed  frames  permitted  the  tube  to  be 
placed  in  definite  locations  relative  to  the  center  of  the  stack.  This 
device,  when  in  service,  caught  everything  excepting  the  lightest  soot, 
which  was  allowed  to  escape  through  the  screen  unaccounted  for. 

Assuming  the  cross-section  of  the  stream  issuing  from  the  stack 
to  be  cut  up,  by  a  series  of  concentric  circles,  into  one  circular  and 
several  annular  areas,  as  shown  in  Fig.  93,  the  small  end  of  the  U  tube 
was  placed  in  the  position  marked  I,  and  held  there  for  thirty  minutes, 
the  sparks  collected  during  this  interval  being  credited  to  this  position. 
The  tube  was  then  moved  to  the  position  II,  where  it  remained  for 
another  period  of  thirty  minutes.  In  like  manner,  it  was  made  to 
occupy  successively  the  positions  III  and  IV,  and  also  the  positions 
Ii,  Hi,  IIIi,  and  IVi,  the  weight  of  sparks  caught  during  each  interval 
being  credited  to  the  corresponding  position  occupied  by  the  small 
end  of  the  tube. 

This  end  of  the  tube  had  an  area  of  2.6  square  inches,  and  it  was 
assumed  that  the  average  weight  of  sparks  passing  through  the  tube, 
while  in  the  positions  I  and  Ilf  would  be  the  same  as  that  passing  any 
area  of  equal  extent  in  the  annular  space  in  which  these  positions  are 


SPARK  LOSSES. 


175 


located.  For  example,  the  outer  annular  area,  comprising  positions  I 
and  Ij,  contained  88  square  inches.  If  in  half  an  hour  0.5  of  a  pound  of 
sparks  were  caught  by  the  tube  in  position  I,  and  in  another  half  an 
hour  0.8  of  a  pound  were  collected  from  the  position  I1;  the  sum  of  these 
two  weights  divided  by  the  area  of  the  sampling-tube  (2.6),  or  .5  of  a 
pound,  would  be  the  average  weight  per  square  inch  per  hour  col- 
lected from  the  two  positions,  and  the  total  weight  for  the  annular 
area  would  be  .5  times  88  or  44  pounds  per  hour.  A  similar  experi- 
ment and  calculation  gave  the  weight  per  hour  delivered  by  each  of 
the  other  annular  areas  II  and  III,  and  by  the  circular  area  IV.  The 


FIB.  93. — Plan  of  Top  of  Stack. 

sum  of  these  separate  determinations  was  assumed  to  be  the  total 
weight  of  sparks  per  hour  delivered  from  the  stack. 

70.  Conditions  of  Tests. — The  series  of  seven  tests  for  which  spark 
losses  were  determined  embrace  a  wide  range  of  conditions,  the  speed 
varying  from  fifteen  to  fifty-five  miles  per  hour,  the  cut-off  from 
twenty-five  per  cent  to  eighty  per  cent  of  stroke,  the  draft  from  two 
inches  to  five  inches  of  water  pressure,  and  the  rate  of  combustion 
from  forty-five  to  one  hundred  and  twenty  pounds  of  coal  per  square 
foot  of  grate  surface  per  hour.  It  will  thus  be  seen  that  the  results 
should  fairly  represent  common  practice.  All  parts  of  the  boiler  and 
engine  were  in  normal  condition,  and  each  test  was  conducted  at  con- 
stant speed  and  load  for  a  sufficient  time  to  permit  accuracy  in  securing 
samples  of  sparks.  The  boiler,  grate,  and  front-end  arrangement  em- 
ployed during  the  tests  are  shown  by  the  drawings  presented  with 
Chapter  III.  The  exhaust-nozzle  was  double,  three  inches  in  diame- 


176 


LOCOMOTIVE  PERFORMANCE. 


ter,  and  the  stack  was  sixteen  inches  in  diameter.     As  in  all  other 
tests  herein  recorded,  the  coal  used  was  Brazil  block. 

71.  Observed  Weight  of  Sparks. — Table  XL.  gives  a  summary 
of  the  observed  data  with  the  tests  arranged  in  order  of  rates  of  com- 
bustion (Column  5),  Test  No.  1  having  the  lowest  rate.  The  laboratory 
symbol  (Column  2)  is  given  to  enable  the  tests  to  be  identified  in  the 
general  presentation  of  data  (Chapter  IV.),  in  case  it  is  desired  to 
compare  boiler  performance  or  other  facts.  The  weight  of  sparks 
passing  from  the  stack  per  hour  and  the  weight  caught  in  the  front  end 
per  hour  are  given  in  Columns  6  and  7  respectively,  while  the  sum  of 
these  two  appears  in  Column  8.  Column  9  gives  the  ratio  of  total 
weight  of  sparks  to  total  weight  of  coal. 

TABLE  XL. 
OBSERVED  VALUES. 


Coal  Fired 

Sparks 

Sparks 

Total 

Ratio  of 

Number. 

Labora- 
tory 
Symbol. 

Draft. 

Coal  Fired 
per  Hour. 

Lbs. 

per  Square 
Foot  of 
Grate  per 
Hour. 
Lbs. 

Passing 
out  of 
Stack  per 
Hour. 
Lbs. 

Caught  in 
Front  End 
per  Hour. 

Lbs. 

Sparks 
per  Hour. 

Lbs. 

Total 
Weight  of 
Sparks  to 
Weight  of 
Coal  Fired. 

1 

2 

3 

4 

5 

6 

7 

8 

9 

1 

15-1-H 

1.93 

791.5 

45.23 

21.9 

12.3 

34.2 

.043 

2 

35-1&-G 

2.98 

1464.8 

83.70 

41.2 

63.2 

104.4 

.071 

3 

35-1-G 

3.02 

1513.6 

86.50 

46.1 

49.9 

96.0 

.063 

4 

35-1-H 

3.00 

1557.1 

88.98 

45.0 

63.4 

108.4 

.070 

5 

55-1-G 

3.57 

1884.4 

107.68 

127.5 

157.2 

284.7 

.151 

6 

35-3-G 

4.88 

2017.7 

115.29 

110.0 

67.3 

177.3 

.088 

7 

15-9-H 

4.99 

2121.0 

121.20 

215.5 

78.0 

293.5 

.138 

Values  given  in  Columns  8  and  9  agree  closely  with  similar  values 
obtained  from  the  special  tests  recorded  in  the  preceding  chapter. 
Thus,  both  series  of  tests  show  large  increase  in  the  spark  loss,  with 
increase  in  rate  of  combustion,  losses  from  this  source  for  the  tests 
under  consideration  being  from  four  to  fourteen  per  cent  of  the  total 
weight  of  coal  fired.  Unlike  the  results  which  are  presented  in  a  pre- 
ceding chapter,  they  were  obtained  under  conditions  common  to  every- 
day service. 

A  graphical  representation  of  the  total  spark  losses,  of  the  proportion 
caught  in  the  front  end,  and  of  the  amount  going  out  of  the  stack  for  the 
several  tests,  is  presented  as  Fig.  94.  The  shaded  portions  represent 
the  sparks  caught  in  the  smoke-box,  the  light  portions  those  passing 
out  of  the  stack.  Referring  to  this  figure  it  will  be  seen  that  in  general 


SPARK  LOSSES. 


177 


the  total  weight  of  sparks  increases  with  the  rate  of  combustion  and 
draft,  and  that  the  proportion  of  sparks  passing  out  of  the  stack,  as  com- 
pared with  those  remaining  in  the  smoke-box,  also  increases.  Test 
No.  1  is  an  exception  to  the  latter  statement,  but  inasmuch  as  the 
total  loss  in  this  case  is  small,  the  record  may  not  be  entirely  trust- 
worthy. In  Test  NOo  2  the  stack  losses  are  less  than  half,  while  in 
Test  No.  7  they  constitute  more  than  two-thirds  of  the  total  loss.  The 
results  of  Tests  Nos.  2,  3,  and  4  are  of  especial  interest,  since  they  were 
run  under  very  similar  conditions,  and  should  therefore  agree  closely. 
Test  No.  5  shows  a  smoke-box  loss  relatively  higher  than  that  of  either 
Tests  Nos.  6  or  7.  This  result,  while  unexpected,  may  be  accounted  for 


Shaded  portions  represent  sparjcs  caught 
in  gmolce-'box,  light  portions  those  pass- 
ing out  of  stack. 


400 
Test  Number 


©  O 


FIG.  94. — Spark  Losses. 


by  the  fact  that  this  was  a  high-speed  test.  Test  No.  6  may  be  more 
nearly  comparable  with  Test  No.  3  than  with  Test  No.  5,  owing  to  the 
high  speed  of  the  latter  test.  The  smaller  values  given  for  Test  No.  6,  as 
'compared  with  those  derived  from  Test  No.  5,  if  not  the  result  of  inaccu- 
racies, must  be  due  to  the  fact  that  the  cut-off  for  this  test  was  consider- 
ably increased,  the  conclusion  being  that  while  the  draft  produced  was 
stronger  and  more  coal  was  burned,  the  effect  of  the  exhaust-jet  was 
less  violent  than  that  of  the  more  rapid  blast  at  high  speed.  The  data, 
however,  is  too  meager  to  be  convincing  upon  this  point,  and  the  con- 
clusion suggested  is  not  in  harmony  with  a  conclusion  reached  as 
a  result  of  a  study  of  the  action  of  the  exhaust-jet  (Chapter  IX.) . 


178 


LOCOMOTIVE  PERFORMANCE. 


The  conclusion  referred  to  is  to  the  effect  that  draft  action  is  in- 
dependent of  speed.  Test  No.  7  was  run  under  a  long  cut-off  with 
the  throttle  partly  closed  and  at  low  speed,  the  condition  being 
such  as  to  give  a  very  strong  exhaust  action.  The  draft  was  greater 
than  for  any  of  the  preceding  tests,  and  more  coal  was  burned  per 
unit  of  time.  The  weight  of  sparks  caught  in  the  smoke-box  is  not 
greatly  in  excess  of  the  weight  caught  in  any  of  the  preceding  tests 
and  is  only  about  half  that  for  Test  No.  5,  but  the  weight  passing  out 
of  the  stack  is  much  greater  than  for  any  other  tests;  the  strong  blast 
evidently  tending  to  clear  the  front  end  of  a  portion  of  the  accumula- 
tion which  otherwise  would  have  lodged  there. 

As  the  total  spark  loss  increased  the  relative  proportion  passing 
from  the  stack  increased,  a  result  which  was  probably  due  in  part 
to  the  strong  scouring  action  incidental  to  heavy  draft  and  to  the 
limited  capacity  of  the  front  end.  It  is  evident,  also,  that  the  Length 
of  the  test  will  have  a  decided  influence  on  the  distribution  of  the  sparks. 
Thus,  in  the  case  of  a  long  test  the  front  end  may  become  completely 
filled,  after  which  all  solid  particles  must  pass  up  the  stack. 

72.  The  Heating  Value  of  the  Sparks  is  disclosed  by  Items  4  and 
5  in  Table  XLI. 

TABLE  XLI. 

EQUIVALENT   COAL. 


Pounds  of  Coal 

Pounds  of  Coal 

Number 

Coal  Fired 
per  Hour. 
Lbs. 

Total  Sparks 
per  Hour. 
Lbs. 

Equivalent  in 
Heating  Value 
to  One  Pound 

Equivalent  in 

Heating  Value 
to  Sparks  per 

Per  Cent  of 
Fuel  Accounted 
for  as  Sparks. 

of  Sparks. 

Hour. 

1 

2 

3 

4 

5 

6 

1 

791.5 

34.2 

.665 

22.7 

2.9 

2 

1464.8 

104.4 

.801 

83.6 

57 

3 

1513.6 

96.0 

.807 

77.5 

5.1 

4 

1557.1 

108.4 

.812 

88.0 

5.7 

5 

1884.4 

284.7 

.841 

239.4 

12.7 

6 

2017.7 

177.3 

.851 

150.9 

7.5 

7 

2121.0 

293.5 

.856 

251.2 

11.9 

,-• 


The  fuel  values  in  equivalent  pounds  of  coal  per  pound  of  sparks 
recorded  in  this  table  were  obtained  in  the  following  manner:  The 
results  of  numerous  analyses  of  sparks  were  plotted  against  the  rates 
of  combustion  at  which  they  were  produced,  and  a  smooth  curve 
was  drawn  as  nearly  as  possible  through  the  points.  This  curve  is 
reproduced  as  Fig.  95.  As  the  experiments  show  that  equal  rates 


SPARK  LOSSES. 


179 


of  combustion  will  produce  sparks  of  equal  heating  value,  the  values 
of  Item  4  were  read  from  the  curve.  Multiplying  Item  4  by  Item  3, 
the  weight  of  coal  equivalent  to  the  spark  loss  per  hour,  Item  5  was 
obtained. 

The  values  of  the  table  confirm  a  conclusion  previously  stated, 
namely,  that  as  the  power  and  rate  of  combustion  increase,  both 
the  total  quantity  of  the  sparks  and  their  heating  value  per  pound 
increase.  Thus  in  Test  No.  1  the  weight  of  sparks  was  about  4  per 


0.90 


0.80   =-£ 


0.70 


Pounds  Coal  per  Square  Foot  of  Grat  >  per  Hou 


FIG.  95. — Heating  Value  of  Sparks. 

cent  of  the  weight  of  the  coal  fired,  and  a  pound  of  the  sparks  was 
equivalent  only  to  four-sixths  of  a  pound  of  coal,  whereas,  in  Test 
No.  7,  when  the  engine  was  working  hard,  about  14  per  cent  by 
weight  of  the  coal  escaped  as  sparks,  and  each  pound  of  sparks  was 
equivalent  to  nearly  five-sixths  of  a  pound  of  coal.  Under  the  con- 
ditions of  this  test,  therefore,  more  than  10  per  cent  of  the  fuel 
which  enters  the  furnace  may  completely  pass  the  heating  surface 
unconsumed. 

73.  Volume  of  Sparks  as  Dependent  upon  Quality  of  Fuel. — 
In  1898,  in  connection  with  locomotive  Schenectady  No.  2,  a  series 
of  tests  designed  to  determine  the  relative  value  of  five  different 
samples  of  coal  were  undertaken  by  the  Engineering  Laboratory  for 
the  C.  C.  C.  &  St.  L.  Railway  Company,  in  connection  with  which  the 
extent  of  spark  losses  was  determined.  The  several  samples  of  coal 
were  designated  as  A,  B,  C,  D,  and  E,  and  the  evaporative  efficiency 


180 


LOCOMOTIVE  PERFORMANCE. 


obtained  from  them  in  locomotive  service  is  that  set  forth  in  Table 
XLIL,  the  values  of  which  are  arranged  in  the  order  of  merit.  From 
the  evaporation  obtained  the  value  of  the  several  samples  may  be 
estimated.  Sample  E  was  a  West  Virginia  coal  of  very  high  quality, 
while  sample  C  was  a  Western  coal,  probably  from  an  Indiana  or 
Illinois  mine. 

TABLE  XLII. 
EQUIVALENT  EVAPORATION. 


Pounds  of  Water  Evaporated  per 
Pound  of  Coal. 

Relative  Value  of  Sample,  calling  the 
Value  of  Sample  E  100. 

of  Sample. 

When  the  Rate 
of  Evaporation 
is  5. 

When  the  Rate 
of  Evaporation 
is  10. 

For  Use  under 
Light  Power. 

For  Use  under 
Heavy  Power. 

I. 

II. 

III. 

IV. 

V. 

E 

10.7 

8.7 

100 

100 

A 

10.0 

8.1 

93 

93 

B 

9.4 

7.7 

87 

89 

D 

8.3 

7.0 

79 

82 

C 

8.5 

7.1 

77 

81 

The  spark  loss  is  assumed  to  be  the  weight  caught  in  the  front  end 
plus  that  which  passes  out  of  the  stack.  Values  for  spark  losses  thus 
obtained  for  the  several  samples  of  coal  tested,  expressed  as  a  per- 
centage of  the  weight  of  coal  fired,  are  presented  in  Columns  II.  and 
III.  of  the  table  below. 

TABLE  XLIII. 
SPARK  LOSSES. 


Designation 
of  Sample. 

Percentage  of  Weight  of  Coal  Fired, 
Accounted  for  as  Sparks  Entrapped 
in  Front   End  and   Passing  out  of 
the  Stack. 

Relative  Weight  of  Sparks  Produced 
by  each  of  the  Several  Samples  in 
Generating    the    Same    Weight    of 
Steam,    assuming    the    Weight    of 
Sparks    resulting  from    Sample   E 
to  equal  100. 

When  the  Rate 
of  Evaporation 
is  5. 

When  the  Rate 
of  Evaporation 
is  10. 

When  the  Rate 
of  Evaporation 
is  5. 

When  the  Rate 
of  Evaporation 
is  10. 

I. 

II. 

III. 

IV. 

V. 

E 
A 
B 
D 
C 

6.6 
6.2 
4.8 
5.7 
3.3 

21.2 
15.6 
16.4 
17.4 
13.8 

100 
101 

84 
109 
65 

100 

79 
87 
100 
80 

SPARK  LOSSES.  181 

From  the  preceding  table  it  appears  that  under  conditions  of 
running  common  in  every-day  service,  from  14  to  21  per  cent  of  the 
coal  fired  disappears  in  the  form  of  sparks  (Column  III).  It  is  true, 
however,  that  the  fuel  loss  is  not  as  great  as  this,  since  the  sparks 
represent  fuel  which  has  been  partially  consumed.  The  sparks  result- 
ing from  the  samples  under  consideration  have  not  been  analyzed, 
but  the  investigations  already  described  indicate  that  they  have  from 
60  to  85  per  cent  of  the  fuel  value  of  a  similar  weight  of  coal.  A 
fair  estimate  of  the  fuel  losses  in  these  tests,  resulting  from  the  passage 
of  sparks  through  the  tube,  may  be  taken  as  75  per  cent  of  the  values 
given  in  Columns  II.  and  III. 

From  a  review  of  the  tables  it  appears  that  those  samples  giving 
the  highest  evaporation  also  give  the  largest  spark  losses.  Two  con- 
ditions probably  account  for  this  fact.  First,  the  purer  coals  are 
lighter,  and  hence  respond  to  the  draft  action  more  easily  than  those 
intermixed  with  non-combustible  matter;  secondly,  in  general,  the 
better  the  coal  the  lighter  the  ash,  a  large  percentage  of  which,  instead 
of  falling  through  the  grate  passes  out  with  the  sparks,  and  adds  its 
mass  to  their  weight. 

It  may  be  urged  as  an  objection  to  those  coals  giving  a  high  ef- 
ficiency, that  their  use  is  attended  by  a  large  spark  loss.  The  argu- 
ment, while  good,  is  not  true  to  the  extent  indicated  by  the  values  in 
Columns  II.  and  III.  For  example,  Column  III.  shows  the  percentage 
of  the  coal  fired,  accounted  for  as  sparks,  but  a  pound  of  sample  C, 
producing  0.138  pound  of  sparks,  did  not  make  as  much  steam  as  a 
pound  of  sample  E,  producing  0.212  pound  of  sparks.  The  relative 
spark-producing  qualities  of  the  several  samples,  based  upon  the  weight 
of  steam  generated,  are  given  in  Columns  IV.  and  V.  These  Aralues, 
therefore,  serve  as  a  logical  basis  from  which  to  determine  the  relative 
spark-producing  qualities  of  the  several  samples. 

74.  Refuse  Caught  in  the  Ash-pan. — Closely  allied  with  the  matter 
of  spark  production  is  that  of  refuse  in  the  ash-pan,  since,  as  already 
noted,  when  the  ash  is  light  much  of  it  passes  up  the  stack.  The 
facts  with  reference  to  ash,  as  applying  to  the  five  samples  of  coal 
dealt  with  in  the  preceding  paragraph,  are  given  in  Table  XLIV. 

The  table  shows  that  when  the  engine  is  running  light,  the  five 
samples  give  nearly  the  same  amount  of  refuse  in  the  ash-pan,  whereas, 
when  the  power  is  increased  to  make  the  rate  of  evaporation  10,  sample 
C  gives  nearly  three  times  as  much  deposit  in  the  ash-pan  as  sample  E. 
In  general  it  may  be  said  that  the  better  the  fuel,  the  less  deposit 


182 


LOCOMOTIVE  PERFORMANCE. 


there  will  be  in  the  ash-pan.  Comparing  the  values  of  Table  XLIV. 
with  those  of  Table  XLIII.  it  appears  that  as  the  character  of  the  coal 
changes  with  reference  to  refuse  in  the  ash-pan,  an  inverse  change 
results  with  reference  to  spark  losses.  Such  a  result  is  logical,  and  is 
quite  in  accord  with  the  explanation  given  in  the  discussion  of  spark 
losses. 

TABLE  XLIV. 
REFUSE  IN  ASH-PAN. 


Relative    Weight    of    Ash    resulting 

Designation 

Percentage  of  Weight  of  Coal  Fired, 
Accounted  for  as  Refuse  in  Ash- 
pan. 

from   Different   Samples   when    the 
Same   Weight   of   Steam   is  Gener- 
ated,   calling  the   Weight  resulting 
from  Sample  E  100. 

of  Sample. 

When  the  Rate 

When  the  Rate 

When  the  Rate 

When  the  Rate 

of  Evaporation 

of  Evaporation 

of  Evaporation 

of  Evaooration 

is  5. 

is  10. 

is  5. 

is  10. 

I. 

II. 

III. 

IV. 

V. 

E 

11.0 

4.9 

100                          100 

A 

10.7 

9.2 

105 

203 

B 

13.9 

11.6 

146 

267 

D 

14.8 

10.3 

170 

257 

C 

14.4 

11.0 

171 

276 

75.  Distribution  of  .Sparks  Throughout  the  Stack. — To  inter- 
cept the  sparks  at  some  point  between  the  front  tube-sheet  and  the 
top  of  the  stack  is  one  of  the  problems  which  confront  designers  of 
draft  appliances.  The  development  of  a  successful  device  for  the  pur- 
pose is  likely  to  be  advanced  by  a  knowledge  of  the  course  taken  by 
the  sparks  in  leaving  the  boiler.  It  is  therefore  thought  proper  to 
present  here  whatever  information  may  have  been  procured  in  the  course 
of  this  investigation  with  regard  to  spark  distribution  in  the  stack. 
For  this  purpose  the  data  of  Test  No.  4,  which  are  considered  to  be  rep- 
resentative, are  presented  graphically  in  Figs.  96,  97,  and  98.  In  Fig. 
96  the  numbers  express  the  weight  of  sparks  passing  out  of  the  stack 
per  square  inch  per  hour  at  the  places  designated,  while  in  Fig.  97 
they  indicate  he  total  pounds  of  sparks  per  hour  passing  each  of  the 
several  areas  into  which  the  stack  was  arbitrarily  divided. 

Comparing  these  results  it  appears  that  the  sparks  follow  the  out- 
side of  the  exhaust  steam  rather  than  the  center.  The  weight  of 
sparks  per  unit  area  increases  steadily  from  the  center  to  the  circum- 
ference, with  the  result  that  ever  50  per  cent  of  the  whole  weight  is 
credited  to  a  ring  two  inches  broad,  measured  from  the  eutsicle  circum- 


SPARK  LOSSES. 


183 


ference,  which  ring  contains  only  about  40  per  cent  of  the  total  area. 
The  velocity  of  the  exhaust  is  necessarily  less  on  the  outside  of  the 
stream,  and,  apparently,  the  sparks  most  readily  follow  the  portion  of 
stream  issuing  from  the  stack  with  the  least  velocity.  In  this  con- 


FIG.  96. — Pounds  of  Sparks  passing 
out  of  Stack  per  Square  Inch  per 
Hour. 


FIG.  97. — Pounds  of  Sparks  passing 
out  of  Stack  per  Hour  in  the  Areas 
Indicated. 


nection  it  should  be  noted  that  these  observations  were  all  made  on 
a  cross-section  of  the  stream  as  it  issued  from  the  stack,  and  therefore 
do  not  necessarily  represent  conditions  actually  existing  in  the  stack. 


FIG.  98. — Cross-section  of  Stack  showing  Density  of  Spark  Discharge. 

76.  The  Size  of  Sparks  varies  with  the  extent  of  the  spark  losses. 
Thus,  under  low  rates  of  combustion,  when  the  total  spark  loss  is 
small,  it  consists  of  a  very  fine,  almost  sooty,  deposit  (A,  Fig.  99). 
but  when  the  total  loss  becomes  large,  the  sparks  themselves  are 
large  (B,  Fig.  99).     Fig.  99  is  a  photograph  of  two  lots  of  sparks,  and 
of  a  pile  of  buckshot,  with  which  the  sparks  may  be  compared.     The 
sample  A  was  obtained  in  Test  No.  1,  when  the  total  loss  was  only  22 
pounds  per  hour,  while  the  sample  B  represents  Test  No.  7,  for 
which  the  loss  was  more  than  ten  times  as  great. 

77.  Conclusion. — The  results  of  the  investigation  described  in  the 
preceding  paragraphs  seem  to  justify  certain  conclusions  which,  while 


184 


LOCOMOTIVE  PERFORMANCE. 


susceptible  of  rather  general  application,  should  nevertheless  be 
accepted  only  for  the  fuels  and  boilers  involved.  Both  locomotives 
involved,  Schenectady  No.  1  and  No.  2,  have  narrow  fire-boxes 
and  a  grate  area  of  about  17.5  square  feet.  The  conclusions  are  as 
follows  : 

1.  The  weight   of  sparks,  which  passes  the  heating  surface  of  a 
boiler  as  cinders  or  sparks,  increases  steadily  with  the  rate  of  com- 
bustion, and  may  reach  a  value  of  from  10  to  15  per  cent  of  the  coal 
fired. 

2.  Sparks  are  composed  of  coals  more  or  less  completely  burned, 
or  they  may  be  wholly  non-combustible,  in  which  case  they  are  entirely 
of  ash. 


FIG.  99. — Sample  Sparks. 


3.  The  fuel  value  per  pound  of  sparks  increases  as  the  total  amount 
increases. 

4.  The  weight  of  sparks  produced  and  the  weight  of  refuse  caught 
in  the  ash-pan  are  inversely  related.     When  the  spark  production  is 
high,  much  of  the  refuse  which  would  otherwise  drop  into  the  ash-pan 
passes  out  from  the  top  of  the  stack. 

5.  The  distribution  of  sparks  throughout  the  cross-section  of  the 
stream  issuing  from  the  stack  is  such  that  the  greatest  weight  of  sparks 
follows  the  slowest  currents  on  the  edges  of  the  stream,  more  than  one- 
half  the  total  weight  passing  through  the  annular  area  which  com- 
prises the  two  inches  nearest  the  stack. 

6.  The  size  of  the  individual  sparks  increases  with  the  total  amount 
produced  up  to  the  limit  allowed  by  the  openings  in  the  netting. 


CHAPTER   X. 

RADIATION  LOSSES. 

78.  The  Amount  of  Heat  Radiated  from  a  locomotive  boiler  is 
necessarily  large,  but  few  attempts  have  been  made  to  measure  it. 
It  is  chiefly  for  this  reason  that  the  experiments  herein  described 
are  of  interest. 

79.  Loss  of  Heat  from  a  Locomotive  Standing  in  a  Building. — 
By  means  of  a  Bristol  recording  pressure-gauge  attached  to  the  boiler 
of  locomotive  Schenectady  No.  1  many  charts  were  obtained,  showing 
the  rate  at  which  the  boiler  pressure  declined  after  the  locomotive 
had  been  shut  down  for  the  day.    These  charts  indicate  that  ordinarily 
the  pressure -would  fall  from  120  to  0  pounds  in  from  12  to  15  hours, 
the  exact  time,  of  course,  depending  upon  many  different  conditions. 

On  January  25,  1895,  at  the  close  of  a  test,  the  water  level  was 
brought  to  the  5"  mark  on  the  glass,  and  the  pressure  noted.  The 
chart  on  the  Bristol  gauge  gave  the  subsequent  record  of  time  and 
pressure.  From  the  known  dimensions  of  the  boiler  and  these  data> 
the  following  was  readily  derived : 

Water  in  boiler,  140.6  cu.  ft ^  8787.5  Ibs. 

Steam  in  boiler  at  110  Ibs.  absolute  pressure,  53.0  cu.  ft.=      13.2  Ibs. 

Total  in  boiler , 8800.7  Ibs. 

Total  weightXheat  of  liquid =  2,685,974  B.  T.  U. 

Weight  of  steamXheat  of  vaporization =       11,565  B.  T.  U. 

The  heat  of  the  steam  is  but  .43  of  one  per  cent  of  the  heat  of  the 
liquid,  and  is  negligible.  In  determining  heat  losses  it  will  be  sufficient 
to  assume  that  the  thermal  units  dissipated  during  any  given  interval 
are  the  product  of  8800  and  the  fall  in 'temperature  in  that  interval, 
Results  thus  derived  are  given  in  Table  XLV. 

185 


186 


LOCOMOTIVE  PERFORMANCE. 


TABLE  XLV. 
HEAT  LOST  FROM  LOCOMOTIVE  BOILER  IN  BUILDING. 

AVERAGE  TEMPERATURE  OF  BUILDING,  71.5°  F. 


Time. 

Absolute 
Pressure  , 
Lbs. 

Temperature, 
Degrees  F. 

Fall  in 
Temperature, 
Degrees  F. 

Fall  in 
Temoerature 
per  Hour, 
Degrees  F. 

B.T.U.  Lost 
per  Hour. 

5.07 

110 

334.56 

5.20J 

100 

327.58 

6.98 

31.02 

273,007 

5.37£ 

90 

320.04 

7.45 

26.64 

234,459 

5.59 

80 

311.80 

8.24 

22.98 

202,247 

6.25£ 

70 

302.71 

9.09 

20.58 

181,125 

6.59 

60 

292.51 

10.20 

18.24 

160,530 

7.40 

50 

280.85 

11.66 

17.04 

149,969 

8.36 

40 

267.13 

13.72 

14.70 

129,374 

9.52 

30 

250.27 

16.86 

13.14 

115,645 

11.45 

20 

227.95 

22.32 

11.88 

104,556 

The  losses  shown  have  by  implication  been  referred  to  as  radiation 
tosses,  but  they  really  include  heat  losses  arising  from  all  sources.  A 
consideration  of  the  methods  employed  will  make  it  evident  that  they 
include  losses  resulting  from  leakage  either  of  steam  or  water.  The 
boiler  itself  is  known  to  have  been  tight,  and  the  throttle  and  other 
valves  are  thought  to  have  been  so,  but  experience  proves  that  in  so 
large  and  complicated  a  structure  as  a  locomotive  boiler  and  its  fittings 
it  is  impossible  to  absolutely  avoid  leakage.  The  locomotive  was  in 
an  exceptionally  good  condition,  and  the  values  given,  are  to  be  accepted 
as  representing  such  losses  as  occur  from  causes  stated  under  most 
favorable  conditions. 

The  coal  equivalent  of  the  heat  lost  may  be  found  by  assuming 
the  boiler  to  absorb  8000  B.T.U.  per  pound  of  coal.  This  assumption 
is  justified  byv  the  facts  presented  in  Chapter  VI.  By  its  use  the 
heat  loss  per  hour  when  the  gauge  shows  95  pounds  pressure  (abso- 
lute 110)  is  equivalent  to 


273007 
8000 


=  34. 1  pounds  of  coal. 


As  the  pressure  and  temperature  fall,  the  heat  loss  diminishes. 

80.  Radiation  Losses  upon  the  Road. — Tests  to  determine  the  heat 
losses  from  the  boiler  of  a  locomotive  on  the  road  were  undertaken 
in  cooperation  with  the  Chicago  &  Northwestern  Railroad  Company 
and  several  manufacturers  of  boiler-covering  in  1898.  The  immedi- 
ate purpose  of  the  test  was  to  disclose  the  relative  value  of  different 


RADIATION  LOSSES. 


187 


materials  employed  in  lagging  boilers,  but  the  plan  was  sufficiently 
broad  to  make  the  results  of  value  in  a  discussion  of  the  more  general 
subject  of  heat  losses  on  the  road.* 

Si.  Plan  of  the  Tests. — In  carrying  out  the  tests  two  locomotives 
were  employed;  one  to  be  hereafter  referred  to  as  the  " experimental 
locomotive"  was  subject  to  the  varying  conditions  of  the  tests;  the 
other  was  at  all  times  under  normal  conditions  serving  to  give  motion 
to  the  experimental  locomotive,  and  as  a  source  of  supply  from  which 
steam  could  be  drawn  for  use  in  maintaining  the  experimental  boiler 
at  the  desired  temperature.  The  experimental  locomotive  was  coupled 
ahead  of  the  normal  engine,  and,  consequently,  was  first,  when  running, 
to  enter  the  undisturbed  air.  The  action  of  the  air-currents  upon 


FIG.   100. — Head  of  Experimental  Train. 

it,  therefore,  was  in  every  way  similar  to  those  affecting  an  engine 
doing  ordinary  work  at  the  head  of  a  train. 

The  boiler  of  the  experimental  locomotive  was  kept  under  a  steam 
pressure  of  150  pounds  by  a  supply  of  steam  drawn  from  the  boiler 
of  the  normal  engine  in  the  rear.  There  was  no  fire  in  the  experimental 
boiler.  It  was  at  all  times  practically  void  of  water.  Precautions 
were  taken  which  justified  the  assumption  that  all  water  of  condensa- 
tion collecting  in  the  experimental  boiler  was  the  result  of  radiation 
of  heat  from  its  exterior  surface.  This  water  of  condensation  was 
collected  and  weighed,  thus  serving  as  a  means  from  which  to  calculate 

*  These  tests  were  outlined  and  conducted  by  the  author  under  the  direction  of 
the  Chicago  &  Northwestern  Railroad  Company,  as  represented  by  Mr.  Robert  Quayle, 
Superintendent  of  Motive  Power,  in  cooperation  with  the  manufacturers  of  various 
materials  employed  as  boiler-coverings.  See  also  "Proceedings  of  Western  Railway 
Club,"  January,  1899. 


188  LOCOMOTIVE  PERFORMANCE. 

the  amount  of  heat  radiated.    The  head  of  the  experimental  train  is 
shown  by  Fig.  100. 

82.  The  Experimental  Boiler  and  its  Equipment. — The  Chicago  & 
Northwestern  locomotive,  No.  626,  the  boiler  of  which  served  in  the 
experiments,  is  of  the  eight-wheeled  type,  weighing  about  90,000 
pounds.  An  outline  drawing,  used  in  ordering  covering,  is  shown  by 
Fig.  101.  The  principal  dimensions  of  the  boiler  are  as  follows : 

TABLE  XLVI. 
DIMENSIONS    OF  BOILER. 

Diameter  in  inches 52 

Heating  surface  (square  feet) 1391 

Total  area  of  exterior  surface,  not  including  surface  of 

smoke-box 358 

Area  of  surface  covered  (square  feet) 219 

Area  of  steam-heated  exposed  surface  not  covered 139 

Ratio  of  surface  covered  to  total  surface .61 

It  should  be  noted  that  the  values  given  in  Table  XLVI.  are  based 
upon  projected  areas  of  the  plain  boiler.  No  account  has  been  made 
of  the  edges  of  plates  at  joints,  nor  of  surface  due  to  the  projection  of 
rivet-heads,  nor  of  the  surface  of  various  attached  projections,  such  as 
running-board  brackets  and  frame  fastenings.  While  all  such  pro- 
jections above  the  general  surface  of  the  boiler  are  active  agents-  in 
conducting  heat  from  the  interior,  the  present  study  does  not  require 
them  to  be  taken  into  account.  The  extent  of  area  covered  for  this 
boiler  is  entirely  normal  for  the  class  of  locomotives  to  which  Xo.  626 
belongs,  which  gives  added  interest  to  the  fact  that  but  61  per  cent 
of  the  exposed  surface  of  the  boiler  was  covered. 

The  whole  grate  of  the  experimental  boiler  was  deadened  by  brick- 
work, and  as  a  further  precaution  against  the  movement  of  air-currents 
through  the  fire-box,  tubes,  etc.,  the  top  of  the  stack  was  securely 
filled  with  wood.  The  furnace  and  front-end  doors  were  also  care- 
fully closed  and  fastened.  A  steam-separator  in  the  supply-pipe  within 
the  cab  of  the  experimental  boiler  was  assumed  to  deliver  to  it  steam 
of  a  uniform  quality.  These  and  other  precautions  justify  the  assump- 
tion that  all  condensation  occurring  in  the  boiler  was  due  to  radiation 
from  its  exterior  surface. 

As  a  safeguard  against  air-pockets  and  to  further  insure  a  uniform 
temperature  of  "all  portions  of  the  interior  of  the  boiler,  steam  was 
allowed  to  waste  from  it  through  a  small  orifice  at  the  end  of  a  pipe 
connecting  with  the  front  end,  and  leading  outside  to  the  top  of  the 


RADIATION  LOSSES. 


189 


I 
I 

i 


190  LOCOMOTIVE  PERFORMANCE. 

stack,  and  some  leak  was  allowed  also  at  the  whistle-valve.  The  loss 
of  steam  from  the  experimental  boiler  in  no  way  affected  the  value 
of  the  measurements  made,  since  they  neither  increased  nor  diminished 
the  amount  of  condensation  taking  place  within  the  boiler. 

A  12-inch  water-glass  was  attached  to  the  water-leg  of  the  boiler 
close  to  the  mud-ring.  A  thread  around  this  glass  served  as  a  reference- 
line.  The  water  condensing  within  the  experimental  boiler  was  led 
through  a  f-inch  pipe  from  the  blow-off  cock  at  the  bottom  of  the 
boiler  to  a  valve  at  the  rear  of  the  cab,  thence  to  the  top  of  the  tender- 
tank,  at  which  point  it  connected  with  a  coil  submerged  in  the  water 
of  the  tank.  The  discharge  from  this  coil  was  delivered  to  a  weighing- 
barrel  set  up  within  the  coal  space  of  the  tender.  By  these  means 
the  water  of  condensation  was  made  a  measure  of  the  amount  of  heat 
radiated,  its  level  was  maintained  constant  a  few  inches  above  the  level 
of  the  mud-ring,  the  excess  was  drained  out,  cooled  to  avoid  all 
chance  of  loss  from  vaporization,  and  weighed. 

As  the  scales  could  not  be  balanced  during  a  run,  and  as  the  weigh- 
ing-tank was  of  insufficient  capacity  to  hold  all  of  the  water  accumu- 
lating during  a  test,  a  calibrated  small-necked  can  was  used  between 
stops  to  reduce  the  level  of  the  water  in  the  barrel.  Each  can,  as 
emptied,  was  charged  against  the  barrel,  a  full  can  counting  45.7 
pounds. 

83.  Observers. — Three  observers  were  ordinarily  employed  during 
each  test.     One  was  assigned  the  duty  of  observing  the  force  and  direc- 
tion of  the  wind,  the  character  of  the  weather,  and  to  so  manipulate 
the   valve    in    the    pipe    through  which   the   condensed   steam  was 
discharged   to  the  weighing-barrel,  that  the  water  level  within  the 
experimental  boiler  would  at  all  times  remain  near  the  reference-line. 
Another  weighed  the  condensed  steam,  and  a  third  recorded  five- 
minute  readings  of  the  steam  pressure  within  the  experimental  boiler, 
and  attended  to  the  discharge  drain  of  the  steam  separator,  in  order 
that   the  water   level  within  this  apparatus   might  be  kept  within 
fixed  limits.     He  also  rang  the  locomotive  bell  for  crossings.     The 
rear  engine  carried  its  usual  crew.     The  train  conductor  also  rode  on 
the  rear  engine. 

84.  The  Track  used  for  the  running  tests  is  a  single  line  extending 
from  Clinton  to  Anamosa,  Iowa,  a  distance  of  seventy- two  miles. 
This  stretch  of  road  was  chosen  because  of  the  light  traffic  upon  it, 
and  the  assurance  against  interruption  which  this  condition  gave. 
It  leads  over  rolling  country,  and  throughout  its  length  is  rather 


RADIATION  LOSSES.  191 

sinuous.  For  the  first  twenty-five  or  thirty  miles  the  general  direction 
is  northwesterly,  and  for  the  remainder  of  the  distance  nearly  west. 
For  four  miles  out  of  Clinton  it  extends  through  the  yards  of  that  city 
and  the  adjoining  city  of  Lyons,  and  for  several  miles  it  follows  along 
the  Mississippi  River,  from  which  it  finally  leads  out  upon  a  more  open 
country.  The  wind  and  temperature  conditions  were  generally  differ- 
ent for  that  portion  of  the  road  along  the  river  than  for  portions  extend- 
ing across  the  more  open  country.  Crossing  stops  were  necessary 
just  beyond  Lyons  and  at  Delmar,  thirty-three  miles  from  Clinton. 
There  are  fifteen  stations  intermediate  between  terminals,  but,  with 
one  exception,  the  plan  of  the  tests  did  not  involve  them. 

85.  Movement  During  the  Tests.— The  work  in  connection  with 
each  covering  occupied  ordinarily  a  single  day.  A  test  under  condi- 
tions of  rest,  hereafter  referred  to  as  a  "standing  test,"  was  first 
made,  followed  by  a  test  on  the  road,  hereafter  to  be  referred  to  as  a 
" running  test." 

Each  running  test  involved  a  trip  from  Clinton  to  Anamosa  and 
return,  with  an  intermediate  stop  each  way  at  the  station  of  Maquo- 
keta,  thirty-eight  miles  from  Clinton  and  thirty-four  miles  from  Ana- 
mosa. By  means  of  these  stops  it  was  possible  to  divide  each  running 
test  into  four  parts  of  nearly  equal  length,  which  not  only  gave  oppor- 
tunity for  ascertaining  something  of  the  character  of  the  results,  which 
were  being  obtained,  but  served  as  a  safeguard  against  the  loss  of  a 
whole  test  in  case  of  an  accident  on  the  road.  For  convenience  these 
parts  of  the  running  tests  are  hereafter  referred  to  as  " quarters," 
but  they  are  not  of  equal  value.  The  quarters  may  be  defined  as 
follows : 

1st  quarter,  Clinton  to  Maquoketa,  38  miles,  approximate  running 
time,  83  minutes. 

2d  quarter,  Maquoketa  to  Anamosa,  34  miles,  approximate  running 
time,  68  minutes. 

3d  quarter,  Anamosa  to  Maquoketa,  34  miles,  approximate  running 
time,  71  minutes. 

4th  quarter,  Maquoketa  to  Clinton,  38  miles,  approximate  running 
time,  84  minutes. 

In  anticipation  of  a  test  the  locomotives  were  coupled,  the  pipe 
connections  made,  and  steam  turned  on  the  experimental  boiler  at 
as  early  an  hour  as  practicable.  In  most  cases  this  was  between  6  and 
7  o'clock  in  the  morning.  After  the  normal  pressure  had  been  secured 
in  the  experimental  boiler,  the  cooling  coil  within  the  tender  was  put 


192  LOCOMOTIVE  PERFORMANCE. 

under  pressure  and  examined  for  leaks.  The  engines  were  then  moved 
to  the  yard  stand-pipe  and  the  tender- tanks  of  both  engines  filled. 
As  soon  as  practicable  after  this,  and  to  insure  the  same  level  of  the 
experimental  boiler  for  all  tests,  the  engines  were  moved  to  a  point 
lower  down  in  the  yard  where  the  rear  driver  of  the  experimental 
engine  rested  over  a  certain  marked  tie.  The  water  within  the  experi- 
mental boiler,  resulting  from  condensation,  was  then  brought  to  the 
reference-line,  time  was  taken,  and  the  scales  of  the  weighing-barrel 
balanced.  At  fifteen-minute  intervals  thereafter  this  process  of 
bringing  the  water  to  line  and  balancing  the  scales  was  repeated, 
usually  for  a  period  of  from  one  to  two  hours,  the  locomotive  remaining 
in  its  place  upon  the  marked  tie.  When  the  rate  of  condensation 
became  uniform  the  standing  test  was  assumed  to  have  commenced. 

In  due  time,  usually  at  about  9:35  in  the  morning,  the  water  was 
brought  to  line  for  the  last  observation  of  the  standing  test,  the  scales 
balanced,  and  as  soon  as  practicable  thereafter  the  engines  were 
started  for  the  running  test.  The  time  of  this  balancing  of  the  weigh- 
ing-tanks marked  the  end  of  the  standing  test  and  the  beginning  of 
the  running  test. 

The  first  few  miles  were,  necessarily,  at  varying  speed,  but  after 
passing  Lyons  and  the  crossing  just  beyond,  a  speed  of  thirty  miles 
an  hour  was  soon  secured,  and  was  thereafter  maintained  until  Maquo- 
keta  was  reached.  In  all  tests  the  stop  at  Maquoketa  was  made  with 
the  rear  tender  under  the  spout  of  the  water-tank,  water  was  taken 
by  the  pushing  engine,  and  the  engines  were  oiled.  While  this  was 
being  done  the  water  of  condensation  in  the  experimental  boiler  was 
brought  to  line  and  the  weighing-barrel  balanced,  thus  ending  the  first 
quarter  and  beginning  the  second  quarter  of  the  running  test.  After  a 
ten  minutes'  stop  start  was  again  made  and  the  run  continued  to 
Anamosa,  where  the  stop  was  made  with  the  rear  driver  of  the  experi- 
mental locomotive  on  a  certain  marked  tie.  As  soon  as  practicable 
thereafter  the  water  was  brought  to  line  and  the  weighing-barrel  bal- 
anced, thus  ending  the  second  quarter  of  the  test. 

At  Anamosa  the  engines  were  uncoupled  and  turned  one  at  a 
time,  coupled  again,  and  the  rear  driver  of  the  experimental  boiler 
brought  over  the  same  marked  tie  upon  which  stop  had  been  made. 
Steam  was  then  turned  on  the  experimental  boiler,  and  the  pressure 
which,  during  the  process  of  turning,  usually  dropped  to  about  eighty 
pounds,  was  restored  to  normal  conditions.  The  start  from  Anamosa 
was  made  at  about  1 :45,  or  an  hour  and  a  half  after  the  scheduled  time 


RADIATION  LOSSES.  193 

of  arriving.  This  interval  gave  time  for  the  work  of  balancing  the 
weighing-barrel,  turning  the  engines,  and  for  dinner;  it  also  gave 
a  sufficient  period,  after  normal  pressure  had  been  restored  in  the 
experimental  boiler,  to  allow  everything  to  become  thoroughly  warm 
before  starting. 

When  all  was  ready  the  condensed  steam  in  the  boiler  was  brought 
to  line,  the  weighing-tank  balanced,  and  the  third  quarter  of  the  test 
thus  commenced.  As  soon  as  practicable  after  the  balancing,  the 
train  was  started  on  the  run  to  Maquoketa,  where,  as  before,  the  stop 
of  ten  minutes'  duration  was  at  the  water-tank.  Here,  again,  the  water 
was  brought  to  line  and  the  weighing-tank  balanced,  thus  ending  the 
third  quarter  and  beginning  the  fourth  quarter  of  the  test,  which 
in  turn  ended  at  Clinton  at  about  4 :30  in  the  afternoon  upon  the  same 
marked  tie  from  which  the  engines  had  been  started  in  the  morning. 

This  process  was  persisted  in  with  regularity,  the  intent  being  to 
secure  similar  conditions  for  each  of  the  several  tests. 

After  the  final  balance  the  tank-valves  of  the  experimental  loco- 
motive were  opened  and  the  tank  drained  to  allow  the  inspection 
of  the  cooling  coil,  which  inspection,  as  already  stated,  preceded  every 
test.  Steam  was  shut  off  the  boiler  and  the  experimental  locomotive 
was  pushed  into  the  roundhouse,  where  men  were  in  waiting  to  strip 
it  of  its  jacket  and  covering.  Early  in  the  evening  work  was  com- 
menced in  applying  the  covering  which  was  to  be  tested  on  the  follow- 
ing day,  and  was  continued  into  the  night  until  finished. 

It  was  found  impossible  to  make  the  running  time  of  all  tests. the 
same.  Conditions  arose  which  could  not  have  been  anticipated. 
There  were  occasional  stops  due  to  section  gangs  and  to  the  presence 
of  other  trains.  Time  which  was  lost  in  this  way  was  not  made  up 
during  the  run,  the  effort  being  to  keep  the  speed  while  running 
constant.  It  is  to  be  noted  also  that  the  running  tests  actually  com- 
menced before  the  train  was  started,  that  the  ten  minutes'  stop  at 
Maquoketa  was  a  part  of  the  running  time,  and  that  the  test  did  not 
end  the  moment  the  engine  stopped,  that  is,  there  was  a  certain  amount 
of  dead  time  on  all  running  tests.  The  facts  in  detail  with  reference 
to  this  are  fully  presented  in  another  place. 

86.  The  Coverings  Tested. — Tests  were  made  in  conjunction  with 
the  bare  boiler  (A),  with  an  old  covering  of  wood  (B)  which  was  on 
the  boiler  when  the  work  began,  and  with  five  different  forms  of  manu- 
factured coverings  designated  as  C,  D,  E,  F,  and  G  respectively.  The 
list  included  all  of  those  materials  now  common  as  insulating  materials, 


194  LOCOMOTIVE  PERFORMANCE. 

as,  for  example,  magnesia,  asbestos,  and  cellular  asbestos  board.  The 
thickness  in  all  cases  was  designed  to  be  the  same  for  all  tests,  but 
the  practice  of  covering  the  surface  of  a  locomotive  boiler,  with  its 
inequalities,  with  material  in  such  thickness  as  will  give  a  smooth 
exterior  surface,  leads  to  variations  in  the  thickness  of  the  covering. 
In  the  boiler  tested  the  dome-casing  was  so  small  as  to  allow  only 
a  thin  layer  (from  i  to  f  in.)  on  the  barrel.  On  other  portions  of  the 
boiler  it  was  intended  that  the  thickness  should  vary  from  If  in.  on 
the  first  ring  to  1J  in.  on  the  slope  sheet.  An  effort  was  made  to 
have  the  thickness  of  all  coverings  tested  the  same,  and,  except  in  two 
cases,  this  result  was  very  nearly  attained. 

As  a  comparative  figure  an  average  thickness  of  all  coverings  was 
obtained  by  finding  the  volume  of  the  material  used,  and  dividing 
this  by  the  area  of  the  surface  covered.  This  process  gives  the  thick- 
ness which  the  material  would  have  had  if  it  had  been  distributed  uni- 
formly over  the  surface  covered.  Values  thus  obtained  are  as  follows: 
Covering  B 1.34  in.  =  1$  in. 

C 1.49in.  =  li|in. 

DI 1.45in.  =  Hf  in. 

"         D2 1.57  in.  =  Hf  in. 

E ' 1.28in.  =  l&in. 

FiandF2 1.56in.  =  Hf  in. 

"         G 1.49  in.  =  l£f  in. 

In  all  cases  the  material  as  above  described  was  covered  by  the 
usual  Russia  iron  lagging. 

87.  The  Tests. — Both  standing  and  running  tests  were  made  with 
the  experimental  boiler  bare,  and  also  w^hen  protected  by  six  dif- 
ferent coverings.     Tests  of  two  of  these  were  repeated,  making  alto- 
gether nine  standing  tests  and  nine  running  tests  to  be  reported. 
These  are  designated  as  follows:   A,  B,  C,  DI,  D2,  E.  FI,  F2,  and  G. 
"A"  represents  the  test-  of  the  bare  boiler.      "Di"  and   "D2"  are 
different  tests  of  the  same  covering,  and,  similarly,  "Fi"  and  "F2"  are 
tests  of  a  single  covering. 

88.  Standing  Tests  and  Results. — All  standing  tests,  save  one, 
immediately  preceded  the  corresponding  running  test.     Standing  Test 
C  followed  the  running  test. 

The  observed  data,  and  the  results  which  have  been  derived  from 
them,  are  presented  as  Table  XLVII.  Most  of  the  lines  in  this  table 
are  self-explanatory,  but  there  are  a  few  which  demand  a  word  of 
explanation. 


RADIATION  LOSSES. 


195 


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196  LOCOMOTIVE  PERFORMANCE. 

No  attempt  has  been  made  to  correct  results  for  different  condi- 
tions of  wind,  but  there  can  be  no  doubt  that  changes  in  exposure 
arising  from  this  cause  had  a  pronounced  effect  upon  the  results  of  the 
standing  test.  For  this  reason  the  results  of  the  standing  test  are 
believed  to  be  far  less  reliable  for  purposes  of  comparison  than  those 
derived  from  the  running  tests  (a  description  of  which  is  to  follow), 
for  in  the  running  tests  the  effect  of  slight  variations  in  wind  velocity 
were  in  the  effect  swallowed  up  of  the  forward  movement  of  the  experi- 
mental boiler  itself. 

The  results  given  for  Test  B  (2.63  pounds  per  minute)  are  so  low 
as  to  be  fairly  open  to  question.  This  was  the  first  test  made.  There 
was  then  nothing  with  which  to  compare  the  results  as  they  were 
obtained.  Basing  an  estimate  on  the  results  of  the  running  test, 
that  for  the  standing  test  should  probably  not  be  less  than  three  pounds 
per  minute. 

These  considerations  emphasize  the  undesirability  of  attaching 
importance  to  the  comparative  showing  made  by  the  different  cover- 
ings during  the  standing  test.  The  collective  showing  is,  however 
of  more  importance. 

89.  Running  Tests  and  Results. — A  complete  summary  of  the  facts 
derived  from  the  running  tests  is  presented  as  Table  XLVIII.  The  fol- 
lowing paragraphs  concern  such  items  in  the  table  as  require  explana- 
tion : 

"Duration  of  Test"  (Item  2).  The  general  process  followed 
throughout  each  of  the  running  tests  has  already  been  described.  As 
has  been  stated,  every  such  test  included  some  time  during  which  the 
engine  was  at  rest.  The  tests  were  started  before  the  train  was 
put  in  motion.  Accidental  stops  operated  to  increase  the  duration 
of  the  test,  and  the  ten  minutes  at  Maquoketa,  during  which  a  balance 
of  the  weighing-tank  was  obtained,  are  included  in  the  recorded  dura- 
tion of  the  running  test.  Finally,  at  the  close,  the  train  came  to  rest 
several  minutes  before  it  was  practicable  to  end  the  test.  The  values, 
therefore,  given  as  Duration  of  Test,  represent  the  whole  time 
between  the  initial  and  final  balancing  of  the  weighing- tank;  it  is 
the  period  for  which  the  record  of  condensed  steam  was  obtained. 

"Actual  Running  Time"  (Item  3).  Under  this  head  appears  the 
number  of  minutes  the  engine  was  actually  in  motion,  and  under  the 
next  head,  "Actual  Standing  Time"  (Item  4),  is  given  the  difference 
between  the  Duration  of  Test  and  the  Actual  Running  Time.  It  will 
appear  further  on  that  the  radiation  losses,  as  observed  for  a  whole 


RADIATION   LOSSES. 


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c.  3d  " 
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RADIATION  LOSSES. 


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Total  condensation  for  test  under  condi- 
tions No.  10  

Assumed  time  during  which  engine  was  run- 
ning, minutes  

Assumed  rate  of  speed,  miles  per  hour  

Assumed  time  during  which  engine  was 
standing.  Duration  of  test  minus  assumed 
time  engine  was  running  =  Item  2e  -  Item  12 

Total  condensation  during  running^  con- 
densation for  test  minus  the  product  of  the 
rate  of  condensation  while  standing  and 
the  assumed  standing  time.  .  . 

Condensation  per  minute  while  running  28.3 
miles  per  hour  

Reduction  in  condensation  per  minute  while 
running  at  a  speed  of  28.3  miles  per  hour, 
resulting  from  covering  applied  to  61%  of 
total  surface  of  boiler,  pounds  

Ratio  of  heat  saved  by  covering  to  total  heat 
transmitted  from  bare  boiler.  . 

l-H 

l-H 

l—  H 

si 

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10 

F-H 

CO 
l-H 

5   1 

GO 

200  LOCOMOTIVE  PERFORMANCE. 

test,  can  readily  be  separated  into  two  parts,  one  applying  to  the 
standing  time  and  the  other  to  the  running  time.  In  this  manner 
results  are  obtained  which  apply  wholly  to  the  conditions  of  running, 
the  effect  of  all  stops  being  eliminated. 

"  Corrections  for  Variations  in  Time  of  Running  and  in  Speed  " 
(Items  12  to  14).  Attention  has  already  been  called  to  the  fact  that 
the  running  tests  are  actually  made  up  of  intervals  during  which  the 
engine  was  in  motion,  and  of  other  intervals  during  which  it  was  at 
rest.  This  being  so,  and  the  time  of  running  and  the  time  of  standing 
being  known,  it  is  easy  to  divide  the  observed  condensation  into  two 
parts,  one  of  which  shall  represent  that  which  resulted  during  the 
period  when  the  engine  was  standing,  and  the  other  that  which  resulted 
during  the  time  the  engine  was  in  motion.  Thus,  the  duration 
(Item  2)  of  Test  B  is  given  as  358.6  minutes,  the  actual  running  time 
(Item  3)  as  313.3  minutes,  and  the  standing  time  (Item  4)  conse- 
quently as  45.3  minutes,  and  the  total  condensation  (Item  11)  is 
1872.3  pounds.  The  rate  of  condensation  while  standing  was  shown 
to  be  2.63  pounds  per  minute  (see  results  from  Standing  Test,  Table 
XLVII).,  so  that  during  the  45.3  minutes  the  engine  was  standing 
119.1  pounds  were  condensed.  The  condensation  while  running,  there- 
fore, would  be  the  total  condensation  minus  the  condensation  while 
standing,  that  is: 

1872.3  pounds  — 119.1  pounds  =  1753.2  pounds. 

A  determination  in  this  general  form  has  been  made  for  all  tests 
in  order  that  the  rate  of  condensation  during  the  running  time  may  be 
shown.  Instead,  however,  of  taking  the  actual  running  time  and 
the  actual  standing  time,  there  has  been  employed  an  assumed  running 
time  (Item  12),  which  is  the  same  for  all  tests,  and  which  is  very  near 
the  actual  time  of  all  tests.  The  adoption  of  this  assumed  running 
time  is  justified  from  the  following  considerations :  If,  for  a  given  test, 
the  running  time  is  slightly  longer  than  for  another  test  with  which 
it  is  to  be  compared,  it  is  evident  that  its  rate  of  speed  was  lower  and 
that  the  air-currents,  as  a  consequence  would,  other  things  being  equal 
be  less  severe  in  their  effect  upon  the  engine.  There  would,  therefore, 
be  injustice  in  determining  the  rate  of  condensation  per  minute  in  the 
two  cases  for  purposes  of  comparison  by  dividing  the  total  condensa- 
tion by  the  observed  time.  If,  however,  the  total  condensation 
observed  during  running  is,  in  each  case,  divided  by  the  same  time, 
the  result  in  each  case  carries  with  it  its  own  correction  for  variations 


RADIATION  LOSSES.  201 

in  speed  of  running.  This  is  the  process  which  has  been  followed 
in  making  up  the  statement  of  results.  At  the  same  time  full  and 
complete  data  are  given  which  will  permit  a  comparison  to  be  made 
on  the  direct  basis,  if  any  are  disposed  to  mistrust  the  assumptions 
already  stated.  The  conclusion  of  this  matter  is  represented  by  the 
" Condensation  per  Minute  while  Running"  (Item  16).  This  factor 
represents,  therefore,  the  observed  condensation  as  corrected  for  varia- 
tions in  steam  pressure,  for  variations  in  atmospheric  temperature, 
and  for  variations  in  speed  of  running.  It  is  probably  as  perfect  a 
basis  upon  which  to  compare  the  merits  of  the  various  coverings  tested 
as  can  be  supplied  by  the  information  obtained  during  the  tests. 
It  is  evident  that  since  all  condensation  must  have  resulted  from  heat 
radiated,  the  smaller  the  amount  of  condensation  the  more  efficient 
the  covering. 

90.  Conditions  Affecting  Results  for  which  no  Corrections  have 
been  Applied  are  to  be  found  in  the  varying  thicknesses  of  covering 
experimented  upon,  and  in  the  varying  velocity  and  varying  direction 
of  the  wind. 

It  may  be  concluded  from  results  obtained  that  corrections  for 
varying  thicknesses,  were  it  practicable  to  derive  them,  would  be 
extremely  small  in  value.  Nevertheless,  the  effect  of  differences  in 
the  thickness  of  the  several  coverings  is  not  in  fact  negligible,  if  results 
are  to  be  directly- compared. 

The  cooling  effect  of  the  wind  will  vary  with  its  velocity  and  direc- 
tion. When  its  direction  is  the  same  as  that  in  which  the  train  travels, 
its  effect  upon  the  locomotive  is  similar  to  that  which  would  be  pro- 
duced if  the  locomotive  were  moving  through  still  air  at  reduced 
speed.  As  each  test  involved  a  round  trip  over  a  given  line  of  track, 
the  direction  of  train  motion  was  reversed  in  the  middle  of  the  test, 
thus  reversing  the  effect  of  the  wind,  the  average  effect  for  the 
whole  test  remaining  practically  the  same  as  though  the  whole 
movement  of  the  locomotive  had  been  in  still  air.  This,  of  course, 
is  strictly  true  only  when  the  direction  of  the  wind  is  in  line  with  the 
track,  but  the  argument  has  force  in  connection  with  all  tests  made. 
The  tabulated  statement  of  condensation  by  quarters  (Item  9),  com- 
pared with  wind  diagrams  (Item  7),  is  instructive  on  this  point.  Thus, 
taking  the  second  and  third  quarters,  from  Maquoketa  to  Anamosa, 
and  from  Anamosa  to  Maquoketa  respectively,  Test  B  shows  a  con- 
stant direction  of  wind  and  a  velocity  of  about  two  miles.  From 
Maquoketa  to  Anamosa,  against  the  wind,  the  condensation  is  452.1 


202  LOCOMOTIVE  PERFORMANCE. 

pounds;  from  Anamosa  to  Maquoketa,  with  the  wind,  the  condensation 
is  410.7  pounds,  a  difference  of  41.4  pounds.  There  can  be  but  little 
doubt  that  the  average  of  the  two  values  will  be  very  close  to  the  result 
which  would  have  been  obtained  had  the  engine  been  running  in  still 
air  once  over  the  line,  at  the  speed  which  prevailed  during  the  test. 

Comparisons  of  this  kind  should  be  made  with  care.  For  example, 
from  considerations  just  presented,  it  would  appear  that  the  condensa- 
tion for  the  last  quarter  should  be  less  than  for  the  first  quarter, 
whereas,  the  uncorrected  data,  with  which  we  are  now  concerned, 
show  it  to  be  greater.  The  explanation  is  to  be  found  in  the  fact 
that  the  return  trip  involved  detentions,  which  made  the  time 
returning  on  the  fourth  quarter  nearly  half  an  hour  longer  than  the 
outward  time  of  the  first  quarter.  The  corrections  for  such  irregu- 
larities have  been  applied  to  the  results  of  the  whole  tests  only,  and 
not  to  the  separate  quarters. 

Returning,  again,  to  a  consideration  of  wind  effects  it  is  to  be  noted 
that  changing  the  direction  of  train  motion  does  not  compensate  for 
the  effect  of  side-winds.  For  this  reason,  such  winds,  even  when 
light,  doubtless  have  a  more  serious  effect  in  impairing  the  com- 
parative value  of  the  results  than  stronger  winds  which  move  along 
the  line  of  the  track. 

Again,  changes  either  in  the  direction  or  velocity  of  wind,  during 
the  progress  of  a  test,  constitute  a  source  of  serious  disturbance.  In 
Test  DI  the  wind  moved  with  the  engine  during  the  first  quarter, 
and,  later  in  the  test,  changed  so  as  to  move  obliquely  with  the  engine 
during  the  return  trip,  with  the  result  that  the  condensation  for  the 
whole  test  is  probably  somewhat  less  than  it  would  have  been  had 
the  direction  remained  unchanged.  A  similar  change  of  wind,  Test  E, 
was  against  the  engine,  its  effect  being  to  give  a  greater  amount  of 
condensation  than  would  have  been  obtained  had  the  wind  remained 
unchanged. 

91.  A  Summary  of  Results. — The  observed  and  calculated  results 
are  given  in  detail  in  Tables  XLVIL  and  XLVIII.  A  summary  of 
these  results  is  here  given  as  Table  XLIX. 

The  values  as  given  have  been  reduced  to  a  common  basis  with 
reference  to  steam  pressure,  atmospheric  temperature,  and  running 
speed,  and,  so  far  as  these  factors  are  concerned,  are  comparable. 
They  have  not  been  corrected  for  variations  in  thickness  of  covering, 
which  in  all  cases  were  slight,  or  for  variations  in  the  velocity  and 
direction  of  the  wind. 


RADIATION  LOSSES. 


203 


TABLE  XLIX. 
POUNDS  OF  STEAM  CONDENSATION  PER  MINUTE. 


A 

B 

C 

A 

D. 

E 

F, 

F, 

G 

(Bare 

Boiler.) 

Standing  test.  .  • 

6.78 

2.63 

3.42 

2.91 

2.80 

3.52 

3.04 

3.22 

3.03 

Running  test.  .  .  . 

14.27 

5.74 

5.47 

5.03 

5.34 

5.21 

5.29 

5.30 

5.70 

Speed,  28.3  miles. 

92.  Efficiency  of  Coverings. — The  percentage  of  the  heat  trans- 
mitted from  the  bare  boiler,  which  is  saved  by  any  covering,  may  be 
obtained  by  subtracting  the  amount  of  condensation  for  the  covering 
in  question  from  the  condensation  for  the  bare  boiler,  and  by 
dividing  one  hundred  times  this  difference  by  the  condensation  for 
the  bare  boiler.  The  result  expresses  the  efficiency  of  the  covering. 
Values  thus  obtained  are  given  in  Table  L. 

TABLE  L. 

EFFICIENCY  OF  COVERINGS  AS  DISCLOSED  BY  RUNNING    TESTS  (PER 

CENT). 


R 

C. 

1), 

D2. 

E. 


G. 


59.8 
61.7 
64.8 
62.6 
63.5 
62.9 
62.8 
60.1 


The  results  of  this  table  are  corrected  for  variations  in  steam 
pressure,  atmospheric  temperature,  and  speed,  but  not  for  variations 
in  weather  and  wind  conditions^  or  for  variations  in  thickness  of  cover- 
ing. The  conclusion  to  be  drawn  from  them,  stated  in  very  general 
terms,  is  that  any  of  the  coverings  tested  can  be  relied  upon  to  save 
from  60  to  64  per  cent  of  all  the  heat  which  would  radiate  from  the 
boiler  were  it  not  covered  at  all.  A  fairly  representative  result  may 
be  stated  as  62.3  per  cent. 

The  fact  that  the  results  obtained  from  the  several  coverings 
are  so  nearly  alike  can  hardly  fail  to  occasion  surprise.     Had  thin 
layers  of  the  material  tested  been  subjected  to  carefully  planned  lab 
oratory  tests,  the  results  would  doubtless  have  differed  more  widely 


204  LOCOMOTIVE  PERFORMANCE. 

but  it  must  be  expected  that  the  value  of  such  difference  will  diminish 
as  the  specimens  experimented  upon  are  increased  in  thickness.  A 
material  which  is  rather  an  indifferent  non-conductor  will  serve  to 
prevent  the  passage  of  heat,  if  applied  in  sufficient  thickness.  While, 
therefore,  the  coverings  tested  were  of  normal  thickness,  it  would  seem 
that  this  thickness  is  sufficient  to  reduce  to  a  negligible  amount  the 
effect  of  the  superior  non-conducting  properties  which  the  material 
of  one  covering  may  have  possessed  over  others. 

The  results  show  that  the  covering  of  61  per  cent  of -the  exterior 
surface  of  the  experimental  boiler  saves  62.3  per  cent  of  all  the  heat 
radiated  from  the  same  boiler  under  similar  circumstances  when  bare. 
It  does  not,  however,  follow  from  this  statement  that  if  100  per  cent 
of  the  exposed  surface  of  the  boiler  were  covered,  102  per  cent  of  the 
heat  lost  from  the  bare  boiler  would  be  saved.  Such  a  conclusion  must 
obviously  be  absurd,  though  a  hasty  consideration  of  the  facts  pre- 
sented might  seem  to  justify  it.  The  fact,  as  first  stated,  however, 
proves  that  there  is  a  vast  difference  in  the  character  of  the  exposure 
to  which  different  portions  of  the  boiler  are  subjected.  While  only  61 
per  cent  of  the  surface  of  the  boiler  was  covered,  the  protection  was 
evidently  applied  where  it  was  most  needed.  The  percentage  of  the 
total  exposure  guarded  against  was  greater  than  the  percentage  of  sur- 
face covered.  For  this  reason  increasing  the  covered  area  by  10  per 
cent  cannot  be  depended  upon  as  a  means  of  reducing  radiation  losses 
by  a  like  amount.  It  will  reduce  loss,  but  the  amount  of  the  reduction 
may  be  very  much  less  than  10  per  cent.  It  is  for  this  reason,  also, 
that  all  comparisons  in  this  report  have  been  based  upon  the  boiler  as 
a  whole.  The  radiation  is  stated  in  terms  of  pounds  of  steam  condensed 
per  minute  for  the  boiler  experimented  upon,  rather  than  as  pound 
per  minute  per  square  foot  of  exposed  surface.  The  latter  unit  would 
be  a  more  general  unit,  but  its  use  in  interpreting  the  data  under  con- 
sideration would  be  misleading. 

93.  Radiation  and  its  Power  and  Coal  Equivalent.  —  Assum- 
ing that  a  locomotive  will  develop  a  horse-power  by  a  consumption  of 
twenty-six  pounds  of  steam  per  hour,  and  assuming  that  the  steam 
thus  consumed  must  be  generated  from  water  at  80°  F.,  the  radia- 
tion losses  already  given  may  be  expressed  in  terms  of  power  losses 
of  equal  value.  The  practical  effect  of  these  assumptions  is  to  define 
a  horse-power  as  equal  to  the  condensation  under  the  conditions  of  the 
tests  of  thirty-four  pounds  of  steam  per  hour,  the  steam  having  a 
pressure  of  150  pounds  and  the  water  the  temperature  due  to  this 


RADIATION  LOSSES.  205 

pressure.     Upon  this  basis  the  following  results  are  obtained.     They 
apply  only  to  the  boiler  tested. 

TABLE  LI. 

POWER  LOST  BY  RADIATION. 

Horse-power  Equiva- 
lent to  Radiation 

Losses. 
Bare  Boiler: 

Locomotive  at  rest  under  conditions  of  test 12 

Locomotive  running  28.3  miles  per  hour  and  otherwise 

under  conditions  of  test 25 

Covered  Boiler: 

Locomotive  at  rest  under  conditions  of  test 4.5 

Locomotive  running  28.3  miles  per  hour  and  otherwise 

under  conditions  of  test 9.3 

Under  ordinary  conditions  of  operation  four  pounds  of  coal  are  con- 
sumed per  horse-power  hour,  hence  the  coal  equivalent  to  the  radiation 
per  hour  may  be  found  by  multiplying  the  values  of  Table  LI.  by 
4.  Thus: 

TABLE  LII. 

COAL  REQUIRED  TO  MAINTAIN  RADIATION  LOSSES. 

Bare  Boiler: 

Locomotive  at  rest  under  conditions  of  test 48  Ibs. 

Locomotive  running  28.3  miles  per  hour  and  otherwise 

under  conditions  of  test 100  Ibs. 

Covered  Boiler: 

Locomotive  at  rest  under  conditions  of  test 18  Ibs. 

Locomotive  running  28.3  miles  per  hour  and  otherwise 

under  conditions  of  test 37  Ibs. 

94.  The  Effect  of  Conditions  other  than  those  which  Prevailed 
during  the  Tests. — The  fact  should  be  emphasized  that  the  results  thus 
far  given  are  those  derived  from  the  actual  experiments.  These  in- 
volved a  boiler  of  moderate  size,  carrying  steam  pressure  which  is  now 
regarded  as  low,  and  were  conducted  in  the  month  of  August.  It 
should  be  noted,  also,  that  the  running  tests  involved  a  speed  of 
less  than  thirty  miles  per  hour.  It  is  evident  that  other  conditions, 
quite  common  to  actual  service,  would  operate  to  greatly  increase  the 
radiation  losses  described.  The  effect  of  changes  in  some  of  these  con- 
ditions will  next  be  considered. 

The  effect  on  radiation  of  changes  in  speed  has  long  been  an  open 
question.  It  has  been  argued  that  a  boiler  perfectly  covered  would 


206 


LOCOMOTIVE  PERFORMANCE. 


be,  to  a  very  great  extent,  unaffected  by  surrounding  air-currents,  and 
hence  tnat  its  radiation  losses  would  not  be  materially  greater  when 
the  locomotive  is  at  speed  than  when  standing.  But  those  who  appre- 
ciate the  intensity  of  the  cooling  currents,  which  circulate  about  a 
locomotive  when  at  speed,  have  been  slow  to  accept  such  a  view,  and 
the  tests  under  consideration  confirm  their  position.  They  give  a 
measure  of  the  radiation  losses,  both  when  the  locomotive  is  at  rest  and 
when  moving  at  a  uniform  speed  of  28.3  miles  an  hour.  While  these 


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10       20      30      40      50      60      70      80      90     100 
FIG.  102.— Effect  of  Speed  on  Radiation  Loss. 

points  are  not  sufficient  to  establish  with  accuracy  the  complete  rela- 
tionship of  radiation  and  speed,  an  estimate  of  real  value  may  be  based 
upon  them.  Such  an  estimate  is  presented  in  the  form  of  a  diagram, 
Fig.  102.  The  diagram  shows  that  the  bare  boiler  when  at  rest  radi- 
ates sufficient  heat  to  condense  6.8  pounds  of  steam,  at  150  pounds 
pressure  per  minute,  which  amount  is  increased  to  twenty-eight  pounds 
when  the  same  boiler  is  driven  at  a  speed  of  eighty  miles  an  hour. 
Similar  values  for  the  covered  boiler  are  3.0  pounds  and  10.6  pounds 
respectively. 


RADIATION  LOSSES.  207 

Changes  in  atmospheric  temperature  would  of  necessity  affect  re- 
sults. Those  recorded  were  obtained  in  midsummer  and  all  have  been 
corrected  for  an  atmospheric  temperature  of  80°  F.  For  each  10° 
reduction  in  atmospheric  temperature  below  80°  the  radiation  may  be 
expected  to  increase  3.5  per  cent.  For  zero  degrees  temperature  the 
radiation  losses  recorded  in  this  report  should  be  increased  by  about 
28  per  cent.  For  example,  if,  when  the  atmospheric  temperature  is 
80°,  the  conditions  are  such  as  result  in  the  condensation  of  five 
pounds  of  steam  per  minute,  when  the  atmospheric  temperature  is  0° 
the  condensation  will  be 

5  +  5(.035X80)=5+1.4  =  6.4. 

From  this  it  appears  that  very  low  temperatures  are  attended  by  radia- 
tion losses  of  considerable  magnitude. 

Changes  in  steam  pressure  also  would  affect  results.  The  ex- 
periments were  conducted  under  a  boiler  pressure  of  150  pounds  by 
gauge.  With  an  increase  of  pressure  the  boiler  temperature  will  be- 
come higher,  and  the  radiation  losses  will,  as  a  consequence,  be  aug- 
mented. Changes  arising  from  this  source,  however,  are  not  great. 
For  each  ten-pound  increase  of  pressure  above  the  limit  of  150  pounds 
the  radiation  may  be  expected  to  increase  by  about  1.6  per  cent,  but 
this  will  not  apply  for  pressures  much  above  200  pounds.  A  pressure 
of  200  pounds  will  involve  losses  by  radiation  which  are  8  per  cent 
greater  than  those  making  up  the  record  of  this  report. 

From  these  considerations  it  can  be  shown  that  with  the  boiler  bare 
and  the  locomotive  running  at  eighty  miles  an  hour,  under  a  steam 
pressure  of  200  pounds,  with  the  atmospheric  temperature  0°,  the 
loss  by  radiation  would  be  the  equivalent  of  sixty-seven  horse-power, 
while  a  covered  boiler,  running  under  the  same  conditions  of  speed, 
pressure,  and  atmospheric  temperature,  would  still  be  subject  to  a  loss 
of  twenty-five  horse-power.  As  a  locomotive  similar  to  that  tested  may 
be  expected  to  deliver  a  maximum  of  600  horse-power,  it  is  evident 
that  under  the  extreme  conditions  just  assumed  at  least  10  per  cent 
of  the  total  power  of  the  engine  would  be  lost  in  radiation.  This  is  for 
an  uncovered  boiler.  An  application  of  any  of  the  coverings  tested 
would  reduce  this  maximum  loss  to  about  4  per  cent. 

Finally,  it  should  be  remembered  that  the  boiler  tested  was  one  of 
moderate  size.  Many  boilers  are  now  running  which  present  an  ex- 
posed area  which  is  at  least  50  per  cent  greater  than  that  presented 
by  the  boiler  under  test,  and  it  should  be  evident  that  the  losses  from 


208  LOCOMOTIVE  PERFORMANCE. 

such  large  boilers  will  be  greater  than  those  disclosed  by  the  tests  under 
consideration.  For  boilers  of  the  same  general  type  the  loss  will  prob- 
ably be  proportional  to  the  exposed  surface. 

95.  Conclusions  concerning  the  extent  of  losses  by  radiation  may 
be  stated  as  follows : 

1.  The  amount  of  heat  radiated  from  the  boiler  of  a  locomotive  in 
motion  is  affected  by  many  different  conditions,  as,  for  example,  by 
the  speed  of  the  locomotive,  the  temperature  of  the  atmosphere,  the 
direction  and  velocity  of  the  wind,  the  steam  pressure,  and  by  the  pro 
portion  of  the  whole  surface  of  the  boiler  which  is  covered. 

2.  The  application  of  a  suitable  covering  to  61  per  cent  of  the  ex- 
posed surface  of  the  boiler  has  resulted  in  a  saving  of  62  per  cent  of  the 
heat  radiated  from  the  uncovered  boiler.     This  does  not  imply  that  if 
the  whole  surface  were  covered  the  radiation  would  be  reduced  to  zero, 
but  rather  that  the  covered  portions  are  those  which  are  most  exposed. 

3.  The  radiation  from  a  given  boiler  is  approximately  twice  as  great 
when  the  locomotive  is  running  thirty  miles  an  hour  as  when  it  is  at 
rest. 

4.  The  loss  from  a  bare  boiler  of  a  locomotive  running  30  miles  an 
hour  is  from  4  to  10  per  cent  of  the  maximum  capacity  of  the  boiler. 
In  summer  it  will  not  much  exceed  the  lower  limit,  in  winter  it  may 
frequently  approach  the  maximum.     An  increase  of  speed  to  60  miles 
will  nearly  double  the  loss. 

5.  The  loss  from  a  boiler  of  a  locomotive  running  30  miles  an  hour 
having  a  considerable  portion  of  its  surface  covered  in  accord  with 
good  practice,  is  from  less  than  1  to  not  more  than  5  per  cent  of  its 
maximum  power.     In  summer  it  will  not  greatly  exceed  the  lower 
limit;   in  winter  it  may  frequently  approach  the  maximum.     An  in- 
crease of  speed  to  60  miles  an  hour  will  augment  the  loss  to  1.3  that 
which  occurs  at  30  miles. 


CHAPTER  XI. 

THE  FRONT  END. 

96.  Definitions. — For  the  purpose  of  this  discussion  the  term 
" front  end"  refers  to  all  that  portion  of  a  locomotive  boiler  which  is 
beyond  the  front  tube-sheet.     It  includes  the  extending  shell  of  the 
boiler  which  forms  the  smoke-box,  and  in  general  all  mechanism  which 
is  therein  contained,  such  as  steam-  and  exhaust-pipes,  netting,  dia- 
phragm and  draft-pipes.     It  also  includes  the  stack. 

The  front  end  as  thus  defined  is  to  be  regarded  as  an  apparatus  for 
doing  work,  receiving  energy  from  a  source  of  power,  and  delivering  a 
portion  thereof  in  the  form  of  a  specific  result.  The  source  of  power  is 
the  exhaust  steam  from  the  cylinders,  and  the  useful  work  accomplished 
is  represented  by  the  volumes  of  furnace  gases  which  are  delivered 
against  the  difference  of  pressure  existing  between  the  smoke-box  and 
the  atmosphere.  That  the  power  of  the  jet  may  be  sufficient,  it  is  neces- 
sary that  the  engines  of  the  locomotive  exhaust  against  back  pressure. 
The  presence  of  the  back  pressure  tends  to  lower  the  cylinder  perform- 
ance, and  it  is  for  this  reason  that  designers  of  front  ends  have  sought 
to  secure  the  required  draft  action  in  return  for  the  least  possible  back 
pressure.  In  other  words,  the  effort  has  been  to  increase  the  ratio  of 
draft  to  back  pressure,  which  ratio  has  been  defined  as  the  efficiency 
of  the  front  end. 

97.  Draft  and  its  Distribution. — The  office  of  the  front  end  is  to 
draw  atmospheric  air  into  the  ash-pan,  thence  through  the  grate  and 
fire,  to  draw  the  furnace  gases  through  the  tubes  of  the  boiler,  thence 
under  the  diaphragm  and  into  the  front  end,  and  to  force  them  out  into 
the  atmosphere.     In  order  that  this  movement  may  take  place,  a  pres- 
sure less  than  that  of  the  atmosphere  is  maintained  in  the  smoke-box, 
so  that  when  the  locomotive  is  working  there  is  a  constant  flow  from 
the  atmosphere  along  the  course  named  and  back  to  the  atmosphere 
again.    The  difference  in  pressure  between  the  atmosphere  and  the 

209 


210 


LOCOMOTIVE  PERFORMANCE. 


smoke-box  is  spoken  of  as  the  draft,  and,  under  normal  conditions  of 
running,  is  represented  by  from  4"  to  10"  of  water. 

It  has  often  been  asked  whether  the  draft,  as  observed  from  gauges 
attached  to  the  front  end,  is  in  any  way  affected  by  changing  the  point 
of  application  of  the  gauge,  a  question  which  is  not  unreasonable  in  view 
of  the  intense  activity  which  characterizes  the  circulation  of  gases 
through  the  front  end.  In  undertaking  a  study  of  the  draft  action  at 
Purdue,  it  was  early  determined  to  settle  this  point.  Elaborate  ap- 
paratus was  prepared  which  would  serve  in  giving  simultaneous  obser- 
vations of  the  pressure  at  several  different  points  within  the  front  end, 
and  which  by  adjustments  which  could  be  quickly  made,  could  be 
arranged  to  apply  to  a  new  series  of  points.  By  the  use  of  this  appara- 
tus it  was  found  possible,  in  a  brief  interval  of  time,  to  explore  thor- 
oughly the  condition  of  pressure  within  the  front  end,  and  to  make 


FIG.  103. — Distribution  of  Draft. 

of  record  the  pressures  at  eighty-four  different  points,  the  time  re- 
quired being  so  short  as  to  leave  no  question  as  to  the  constancy  of  the 
running  conditions.  Many  different  sets  of  observations  thus  obtained 
justified  the  conclusion  that,  so  far  as  the  space  in  front  of  the  dia- 
phragm is  concerned,  draft-gauges  attached  at  any  points  will  all  show 
identical  readings.* 

The  distribution  of  draft  throughout  the  apparatus  intervening  be- 
tween the  front  end  and  the  ash-pan  is  a  matter  of  more  than  ordinary 
interest.  Its  value,  as  determined  when  the  locomotive  was  operating 
under  three  different  rates  of  power,  is  shown  by  Fig.  103.  Calling 

*  For  a  detailed  description  of  this  work  see  "American  Engineer,"  May,  1902. 
p.  131. 


THE  FRONT  END. 


211 


the  ash-pan  pressure  zero  and  referring  to  the  40-mile  curve  of  this 
diagram,  the  draft  in  the  fire-box,  as  measured  by  a  gauge  attached  to 
a  hollow  stay-bolt,  is  1.5"  of  water,  between  the  front  tube-sheet  and 
the  diaphragm  (section  H)  it  is  3",  and  between  the  diaphragm  and 
the  base  of  the  stack  (section  F)  it  is  5".  The  last  value  is  that 
which  is  usually  measured  and  referred  to  as  the  "draft."  The  per- 
centage of  the  total  draft  absorbed  by  various  portions  of  the  system 
is  shown  by  Table  LIII. 

TABLE  LIII. 
PERCENTAGE  OF  TOTAL  DRAFT  REQUIRED. 


Speed,  Miles 
per  Hour. 

To  Draw  Air 
into  Fire-box. 

To  Draw  Smoke 
and  Gases  through 
Tubes. 

To  Draw  Smoke 
and  Gases  under 
Diaphragm. 

20 

22.6 

41.1 

36.3 

30 

30.1 

33.6 

36.3 

40 

30.4 

32.0 

37.6 

It  will  be  seen  that  the  relative  resistance  of  different  portions  of 
the  system  varies  but  little  under  changes  in  speed.  More  than  one- 
third  of  the  total  draft  value  is  absorbed  in  drawing  the  gases  past  the 
diaphragm,  approximately  another  third  is  absorbed  in  the  passage  of 
the  tubes,  and  the  remainder  is  available  for  drawing  air  from  the  ash- 
pan  through  the  grate  and  fuel  into  the  fire-box.  It  is  really  this  latter 
value  only  which  promotes  combustion.  Under  present  conditions  of 
operation,  it  is  thought  necessary  as  a  matter  of  practical  importance 
to  have  the  opening  under  the  diaphragm  ocmparatively  small,  in 
order  that  the  velocity  of  the  gases  may  be  sufficiently  high  in  passing 
to  clear  the  front  end  of  cinders.  The  results  show  that  the  cost  of 
this  self-clearing  action,  as  measured  in  the  draft  absorbed,  is  so  great 
as  to  suggest  the  possibility  of  a  material  improvement  in  design  at 
this  point.  If  the  diaphragm  could  be  abandoned,  or  if  the  area  under 
it  could  be  materially  increased  without  introducing  new  difficulties, 
the  efficiency  of  the  front  end  could  be  greatly  improved. 

It  is  often  assumed  that  a  locomotive  having  a  wide  fire-box  and 
large  grate  can  be  operated  with  a  larger  exhaust-tip  than  one  having 
a  narrow  fire-box  and  smaller  grate  and  that  since  the  larger  grate  per- 
mits a  given  amount  of  fuel  to  be  burned  at  a  lower  rate  of  combustion, 
the  work  which  the  steam-jet  has  to  do  is  diminished.  Experience  on 
the  road,  on  the  other  hand,  has  shown  that  differences  in  grate  area 
do  not  necessarily  involve,  or  ordinarily  permit,  changes  in  the  draft 


212  LOCOMOTIVE  PERFORMANCE. 

appliances.  The  reason  for  this  is  to  be  found  in  the  fact  that,  whether 
the  grate  be  large  or  small,  two-thirds  of  the  difference  in  pressure 
between  the  front  end  and  the  atmosphere  is  absorbed  in  moving  the 
air  and  gases  through  the  tubes  and  under  the  diaphragm.  The  vol- 
ume of  air  and  gases  to  be  moved  is  not  materially  changed  by  chang- 
ing the  area  of  the  grate,  and  while  the  difference  in  pressure  between 
the  atmosphere  and  the  fire-box  will  be  less  with  the  large  grate  than 
with  the  small  one,  this  difference  is  insignificant  in  amount  when  com- 
pared with  the  total  draft  action  which  is  required  to  stimulate  the 
movement  through  the  remaining  portion  of  the  systems. 

98.  The  Action  of  the  Exhaust- jet. — A  study  of  the  foim  and  ac- 
tion of  the  jet  of  exhaust  steam  in  the  front  end  of  a  locomotive  was 
undertaken  at  the  Purdue  Laboratory,  in  cooperation  with  a  commit- 
tee of  the  Master  Mechanics'  Association.*  Prior  to  this  time  it  had 
been  common  to  assume  that  the  action  of  the  exhaust-jet  was  similar 
to  that  of  a  pump,  that  the  exhaust  from  each  cylinder-end  supplies 
a  ball  of  steam  which  fills  the  stack  very  much  as  the  piston  of  a  pump 
fills  its  cylinder,  and  which,  by  virtue  of  its  own  momentum,  pushes 
before  it  a  certain  volume  of  the  smoke-box  gases  until  it  passes  out 
of  the  top  of  the  stack.  In  obedience  to  this  theory,  experimenters 
had  sought  to  so  design  their  apparatus  that  the  spread  of  the  jet  would 
be  sufficient  to  fill  the  stack  at  its  base.  A  knowledge  of  the  form  of 
the  jet  was  therefore  regarded  as  of  prime  importance.  With  this 
understanding  of  the  general  problem  the  Purdue  laboratory  entered 
upon  its  work. 

The  apparatus  employed  is  shown  in  part  in  connection  with  Fig. 
104,  which  is  a  drawing  to  scale,  showing  a  cross-section  through  the 
center  of  the  stack  of  the  front  end  experimented  on.  In  line  with  the 
center  of  the  stack  and  exhaust-pipe,  cast-iron  sleeves  .were  fastened 
to  the  outside  of  the  smoke-box.  Through  these  were  fitted  pipes  1, 
2,  3,  4,  and  5,  arranged  to  slide  in  and  out  across  the  smoke-box,  and 
having  their  inner  ends  turned  down  to  a  fine  tip  with  sharp  edges,  and 
the  edges  bounding  the  orifices.  The  body  of  each  pipe  was  graduated 
to  tenths  of  inches,  the  scale  reading  from  a  reference-mark  fixed  to 
the  sleeve  on  the  outside  of  the  smoke-box.  If  the  zero  of  the  scale 
were  brought  under  the  reference-mark,  the  inner  tip  of  the  pipe 
would  be  directly  under  the  center  of  the  stack;  that  is,  directly  over 


*  For  a  full  account  of  the  important  work  accomplished  by  this  committee, 
see  "Proceedings  of  the  American  Railway  Master  Mechanics'  Association,"  Vol. 
XXIX.,  1896. 


THE  FRONT  END. 


213 


FIG.  104. 


214  LOCOMOTIVE  PERFORMANCE. 

the  center  of  the  exhaust-pipe.  It  is  obvious  that  if  the  tip  of  any 
pipe  be  surrounded  by  the  jet  of  exhaust  steam,  the  velocity  of  the 
latter  will  tend  to  carry  steam  through  the  pipe  and  to  discharge  it 
into  the  atmosphere  outside  of  the  smoke-box.  It  can  be  shown  also 
that  the  force  which  the  steam  would  exert  in  its  effort  to  pass  the 
pipe  is  a  function  of  its  velocity;  hence,  by  observing  the  force  or  pres- 
sure, the  velocity  may  be  calculated.  Pressures  were  observed  by 
having  the  outer  ends  of  each  sliding-pipe  connected  by  rubber  tub- 
ing with  one  leg  of  a  manometer  or  U  shaped  glass  tube,  which  Avas 
fastened  to  the  wall  of  the  laboratory.  These  U  tubes  were  partially 
filled  with  mercury,  the  displacement  of  which  gave  the  pressure  trans- 
mitted through  the  tube.  If,  for  example,  the  tip  of  any  particular 
pipe  were  in  the  jet  of  steam,  its  manometer  would  show  pressure 
greater  than  that  of  the  atmosphere;  if  it  were  withdrawn  from  the 
jet  its  manometer  would  indicate  a  pressure  less  than  that  of  the 
atmosphere.* 

Besides  these  sliding-pipes  in  the  smoke-box,  the  stack  was  fitted 
with  three  pipes  which  had  plain  ends  projecting  beyond  the  inner  wall 
about  a  quarter  of  an  inch.  These  side  orifices  were  each  connected 
with  a  manometer.  They  served  to  show  the  extent  of  pressure  or 
vacuum  existing  within  the  stack  at  points  where  they  were  attached. 
Their  exact  location  is  shown  by  the  dimensions  in  Fig.  104. 

The  normal  draft  was  measured  by  two  different  manometers  con- 
nected with  the  front  end,  and  was  permanently  registered  by  a  Bristol 
recording-gauge.  Indicators  were  used  to  show  the  steam  distribu- 
tion in  the  engine  cylinders,  and  a  special  indicator  fitted  with  a  light 
spring  gave  a  fine  record  of  the  back-pressure  line.  This  pressure  was 
also  recorded  by  a  Bristol  gauge.  A  Boyer  speed-recorder  served  as  a 
means  for  maintaining  constant  speed  conditions. 

Observations  were  made  as  follows:  Desired  conditions  of  speed 
and  steam  pressure  having  been  obtained,  the  adjustable  pipes  (1,  2, 
3,  4,  and  5),  Fig.  104,  were  withdrawn  from  the  smoke-box  sufficiently 
to  bring  them  entirely  clear  of  the  exhaust-jet,  usually  to  a  distance 
of  4*  :nches  from  center  of  jet.  Then,  upon  signal,  all  manometer 
gauges  were  read  and  all  other  observations  taken,  the  readings  being 
taken  simultaneously.  Each  sliding-pipe  was  then  moved  inward  a 
tenth  of  an  inch  and  readings  repeated,  after  which  they  were  moved 

*  See  "A  Gliinpse  of  the  Exhaust-pipe,"  Proceedings  of  the  Western  Railway 
Club  for  October,  1895. 


THE  FRONT  END.  215 

another  tenth,  and  so  on  until  the  tip  of  all  the  pipes  reached  the  center 
of  the  exhaust-jet.  The  readings  thus  obtained  from  the  pipes  1,  2, 
3, 4,  and  5,  Fig.  104,  were  entered  upon  a  half-sized  drawing  represent- 
ing a  portion  of  the  cross-section  of  the  smoke-box,  the  position  of  each 
entry  showing  the  exact  location  to  which  the  numerical  readings 
applied.  Upon  the  diagram  of  pressures  thus  obtained  lines  were 
drawn  through  points  for  which  the  pressure  was  zero.  These  lines 
were  assumed  to  represent  the  border  of  the  steam-jet.  Reduced  in 
scale,  they  are  the  full  lines  given  in  Figs.  107  to  118,  the  full  signifi- 
cance of  which  is  to  be  hereafter  considered.  Next,  lines  were  con- 
structed by  connecting  points  showing  a  pressure  of  0.5  inch  of  mer- 
cury, and  still  other  lines  by  connecting  points  representing  a  pressure 
of  1.5  inches  of  mercury;  and,  finally,  in  some  cases  the  curves  corre- 
sponding with  2.5  inches  of  mercury  were  located.  These  lines  of  equal 
pressure  are  those  which  appear  in  Figs.  107  to  118,  but  the  numbers 
given  in  connection  therewith  represent  the  velocity  in  feet  per -second, 
as  calculated  from  the  pressure  already  noted.  The  curves  are,  in 
fact,  equal  velocity  curves  as  well  as  curves  of  equal  pressure. 

Confining  the  discussion  for  the  present  to  matters  affecting  the 
action  of  the  jet,  it  may  be  said  with  certainty  that  the  exhaust-jet 
acts  upon  the  smoke-box  gases  (1)  to  induce  motion  in  those  portions 
which  immediately  surround  it,  and  (2)  to  enfold  and  entrain  the 
gases  which  are  thus  made  to  mingle  with  the  substance  of  the  jet 
itself. 

The  induced  action,  which,  for  the  jets  experimented  upon,  is  by 
far  the  most  important,  may  be  illustrated  by  means  of  Fig.  105.  The 
arrows  in  this  figure  represent,  approximately,  the  direction  of  the  cur- 
rents surrounding  the  jets.  It  will  be  seen  that  the  smoke-box  gases 
tend  to  move  toward  the  jet,  and  not  toward  the  base  of  the  stacks,  at 
which  point  they  are  to  leave  the  smoke-box.  That  is,  the  jet,  by 
virtue  of  its  high  velocity  and  by  its  contact  with  surrounding  gases, 
gives  motion  to  particles  close  about  it,  and  these,  moving  on  with  the 
jet,  make  room  for  other  particles  which  are  farther  away.  As  the 
enveloping  shell  of  gas  approaches  the  top  of  the"  stack  its  velocity 
decreases  and  it  becomes  thinner  and  thinner,  all  as  shown  by  Fig.  105. 
All  parts  of  the  jets  require  gases  to  work  upon,  the  upper  as  well  as  tho 
lower  part.  Gauges  attached  to  the  side  of  the  stack  show  a  vacuum, 
because  the  gases  needed  for  the  upper  portion  of  the  jet  can  reach  it 
only  by  coming  in  around  the  jet  lower  down.  In  other  words,  the 
action  of  the  upper  part  of  the  jet  induces  a  vacuum  in  the  lower  part 


216 


LOCOMOTIVE  PERFORMANCE. 


of  the  stack,  just  as  the  action  of  the  jet  as  a  whole  induces  a  vacuum 
in  the  smoke-box.    It  will  be  shown  later  that  as  the  amount  of  work 


FIG.  105. 

to  be  done  by  the  exhaust  is  increased  the  jet  becomes  smaller,  thus 
making  room  for  larger  volumes  of  gas  to  pass  between  it  and  the 


THE  FRONT  END. 


217 


stack;  the  velocity,  both  of  the  jet  and  of  the  induced  currents,  in- 
creasing. It  is  of  interest  in  this  connection  also  to  note  that  of  the 
gauges  attached  to  the  side  of  the  stack  (Fig.  105),  a,  which  is  13  inches 
above  the  base,  always  gave  about  one  and  one-half  (1.5)  times  the 
reduction  of  pressure  which  was  recorded  by  the  gauge  attached  to  the 
smoke-box,  and  that  the  second  gauge,  which  is  10  inches  from  the  top 
of  the  stack,  gave  approximately  six-tenths  (0.6)  of  the  value  recorded 
in  the  smoke-box. 

That  there  is  some  intermingling  of  the  smoke-box  gases  with  the 
steam  of  the  jet  is  made  evident  by  the  appearance  of  the  combined 
stream  as  it  issues  from  the  top  of  the  stack.  The  manner  in  which 
this  intermingling  takes  place  will  be  seen  from  the  following  consid- 
erations : 

Any  stream  flowing  from  a  nozzle  through  a  resisting  medium  will 
have  a  higher  velocity  at  its  center  than  at  its  circumference  or  sides, 
that  is,  the  particles  at  the  center  of  the  jet  move  at  a  higher  velocity 
than  those  on  the  outside,  the  latter  being  held  back  by  contact  with 
the  surrounding  gas.  The  result  of  the  different  velocities  in  the  same 
stream  is  a  wave  motion  of  the  individual  particles  of  which  the  stream 
is  composed.  Thus,  the  path  of  any  one  of  these  particles  may  be 
shown  by  Fig.  106,  B,  but  the  exact  form  and  frequency  of  the  loops 


FIG.  106. 


will  depend  upon  the  relation  between  these  differences  in  the  velocity 
of  particles  in  different  portions  of  the  stream  and  the  actual  mean 
velocity  of  the  jet.  If  the  velocity  of  the  jet  is  high,  and  differences 
for  different  portions  of  the  cross-section  are  not  great,  the  loop  may 
disappear,  the  path  appearing  as  shown  by  Fig.  106,  A.  With  a  still 


218  LOCOMOTIVE  PERFORMANCE. 

higher  mean  velocity  and  a  smaller  difference  the  loops  would  ap- 
proach the  form  shown  by  Fig.  106,  C.  The  exhaust-jet  appears  to  take 
this  latter  form.  Measurements  to  determine  its  velocity  show  that 
particles  in  the  center  move  much  more  rapidly  than  those  near  the 
outside,  and  other  measurements  to  determine  the  form  of  the  jet  as 
a  whole  define  a  boundary  which  is  neither  a  straight  line  nor  a  regu- 
lar curve,  but  which  agrees  closely  with  the  form  given  by  Fig.  106,  C. 
All  this  shows  that  the  jet  is  stepped  off  in  nodes,  which  under  given 
conditions  remain  fixed  in  position.  This  conclusion,  based  upon  meas- 
urements of  the  jet,  is  confirmed  by  the  appearance  of  the  jet  as  seen 
in  an  engine  running  with  the  front  end  open.  The  jet,  when  thus 
viewed,  exhibits  one  or  more  bright  spots  which  remain  in  a  fixed  posi- 
tion. It  is  through  the  wave-like  action  of  the  particles  making  up 
the  steam-jet  that  the  surrounding  gases  are  intermixed  with  the  jet. 

It  is  clear  that  any  design  of  nozzle  which  will  serve  to  subdivide 
the  stream,  or  to  spread  it  so  as  to  increase  its  cross-section,  will  assist 
the  jet  in  its  effort  to  entrain  the  gases,  but  it  is  not  clear  that  there 
is  any  gain  to  be  realized  in  such  a  result.  It  is  possible  that  as  the 
mixing  action  is  increased  the  induced  action  may  be  diminished,  and 
that  the  sum  total  of  the  effect  produced  may  remain  nearly  constant. 
The  work  which  has  thus  far  been  done  is  not  conclusive  on  this  point, 
but  the  evidence  tends  to  show  that  the  more  compact  and  dense  the 
jet  the  higher  its  efficiency.  It  is  certainly  clear  that  for  the  jets  ex- 
perimented upon  the  mixing  action  is  hardly  more  than  incidental  to 
the  induced  action,  the  latter  constituting  the  influence  through  which 
the  work  of  the  jet  is  chiefly  accomplished. 

The  similarity  existing  between  the  action  within  the  front  end  of 
a  locomotive  and  that  within  an  injector  will  at  once  suggest  itself, 
but  the  resemblance  is  not  perfect.  In  an  injector  the  jet  of  steam 
is  almost  immediately  and  completely  condensed.  It  loses  its  iden- 
tity by  intermixing  with  the  water  to  which  it  imparts  its  energy.  The 
mixture  is  complete  before  the  water-orifice,  through  which  the  com- 
bined stream  must  pass,  is  reached.  In  the  front  end  of  a  locomotive, 
on  the  other  hand,  the  mixing  of  the  jet  with  the  stream  of  gas  upon 
which  it  acts  proceeds  but  slowly,  and  with  the  apparatus  now  in  use ; 
it  is  doubtful  if  the  process  is  ever  completely  accomplished. 

99.  Form  and  Character  of  the  Jet. — In  Figs.  107  to  118  the  steam- 
jet  is  represented  by  a  series  of  lines.  The  full  or  outside  lines  are 
assumed  to  represent  the  boundary  of  the  jet.  They  do,  in  fact,  pass 
through  points  for  which  the  velocity  of  the  steam  and  gases  is  so  low 


THE  FRONT  END. 


that  their  impress  upon  the  bent  tubes  is  only  sufficient  to  balance 
the  pressure  of  the  atmosphere.  Each  dotted  line  inside  of  those 
already  referred  to  passes  through  a  series  of  points  where  the  velocities 
are  equal,  the  value  of  which  in  terms  of  feet  per  second  is  given.  A 
comparison  of  the  form  and  location  of  similar  lines  in  different  dia- 
grams will  show  the  effect  produced  by  the  different  combinations  of 
mechanism  employed. 

100.  The  Jet  as  Affected  by  Changes  in  Speed  of  the  Locomotive. 
— The  three  jets  shown  by  Figs.  107  to  109,  inclusive,  were  obtained 


MILES  PER  HOUR 


FIG.  107. 


MILES  PER  HOUR  3$ 

REVOLUTIONS  PER  MINUTE  188 

POUNDS  Of  .STEAM  PER  HOUR     81?2 


FIG.  108. 


MILES  PCR  HOUR  4» 

REVOLUTIONS  PER  MINUTE  *4» 

POUNDS  Of  STEAM  PER  HOUR      867O 


FIG.  109. 


under  similar  conditions,  except  that  for  Fig.  107  the  speed  was  25 
miles  per  hour;  for  Fig.  108,  35  miles;  and  for  Fig.  109,  45  miles. 
Each  increment  of  speed  results  also  in  a  larger  volume  of  steam  de- 
livered, and,  consequently,  a  greater  reduction  of  pressure.  The  dia- 
grams show  that  the  rapidity  of  the  exhaust  impulse  does  not  greatly 
affect  the  character  of  the  interior  of  the  jet,  also  that  the  spread  of 
the  jet  diminishes  as  the  speed  is  increased;  or,  in  other  words,  as  the 
volume  of  steam  passing  the  nozzle  becomes  greater,  the  increased 


220  LOCOMOTIVE  PERFORMANCE. 

velocity  of  both  the  jet  of  steam  and  the  body  of  gas  immediately  sur- 
rounding it,  together  with  the  reaction  of  the  latter,  probably  consti- 
tute the  causes  which  operate  to  narrow  the  jet.  The  velocity  curves, 
which  in  Fig.  108  are  pretty  evenly  distributed  throughout  the  body  of 
the  jet,  are  in  Fig.  109  crowded  together,  giving  evidence  in  the  latter 
case  of  a  very  dense  and  powerful  jet.  The  results  show  that  the  more 
rapidly  moving,  though  smaller,  jet  (Fig.  109)  is  more  effective  in  pro- 
ducing draft  than  that  which  is  shown  by  Fig.  107. 

101.  The  Effect  upon  the  Jet  of  Changes  in  the  Height  of  the 
Bridge. — An  essential  feature  of  the  single  exhaust-pipe  is  the  so-called 
bridge,  which  maintains  a  separate  steam-passage  for  each  cylin- 
der for  a  "portion  of  the  length  of  the  pipe.  It  is  above  the  top  of 
this  bridge  only  that  the  steam  exhausted  from  both  sides  of  the  loco- 
motive intermingles.  The  purpose  of  the  bridge  is  a  twofold  one: 
it  prevents  the  exhaust  of  one  side  from  blowing  through  into  the  ex- 
haust-passage of  the  other  side,  and  when  properly  designed  it  is  the 
means  of  making  that  side  from  which  the  strongest  stream  is  passing 
assist  by  induction  the  exhaust  from  the  other  side.  To  determine 
the  best  height  of  bridge  exhaust-pipes  of  four  different  designs 
were  tested  by  the  Master  Mechanics'  Committee,  all  being  the  same 
except  in  the  height  of  the  bridge  and  in  the  proportions  of  those  parts 
adjacent  thereto.  Two  nozzles  representing  the  extreme  conditions 
with  reference  to  this  detail  were  employed  in  experiments  designed 
to  determine  the  character  of  the  jet,  with  results  which  are  to  be  seen 
by  comparing  Figs.  107  to  109  with  Figs.  110  to  112.  Figs.  107  and 
110  represent  identical  conditions,  except  as  to  the  height  of  the  bridge, 
as  do  also  Figs.  108  and  111,  and  Figs.  109  and  112.  An  examination 
of  the  velocity  curves  of  these  figures  will  show  that  for  similar  condi- 
tions of  running  the  jet  for  the  two  groups  is  nearly  identical.  It  will 
be  of  interest  to  add  that,  basing  their  conclusions  upon  efficiency 
tests  made  at  Chicago,  the  committee  concluded  that,  whenever  the 
bridge  was  less  than  12",  some  loss  of  efficiency  resulted,  though  such 
loss  was  not  great  even  when  the  height  of  the  bridge  was  reduced  to 
5".  They  recommend  that  the  bridge  be  not  less  than  12".  They 
recommend,  also,  that  where  long  exhaust-pipes  must  be  employed, 
the  increased  length  should  always  be  secured  by  extending  that 
portion  of  the  pipe  which  is  above  the  bridge.  This  recommendation 
in  effect  contemplates  a  constant  height  of  bridge  for  all  lengths  of  pipes. 

To  the  discussion  with  reference  to  the  bridge  it  will  be  of  interest 
to  add  some  reference  to  the  "choke." 


THE  FRONT  END. 


221 


That  part  of  the  steam-pipe  between  the  bridge  and  the  outside 
wall,  where  the  contraction  of  the  passage  is  greatest,  has  generally 
been  referred  to  as  the  choke.  An  early  committee  had  recom- 
mended that  the  area  of  the  choke  be  80  per  cent  of  that  of  the 
nozzle,  and  the  committee  of  1896  did  a  large  amount  of  work  upon 
pipes  having  this  proportion.  Not  satisfied,  however,  with  the  valid- 
ity of  the  conclusions,  the  later  committee  extended  its  research  to 
involve  a  large  range  of  proportions,  with  results  sustaining  the  con- 


fOUNDS  OF  STEAM  PER  HOUR      «090 


FIG.  110. 


ILES  PER  HOUR  4* 

POUNDS  OF  STEAM   PER  HOUR      «(?» 


FIG.  111. 


FIG.  112. 


elusions;  first,  that  the  area  of  the  choke  should  not  be  less  than  the 
area  of  the  nozzle;  and,  second,  that  whenever,  with  a  given  pipe,  it 
is  necessary  to  sharpen  the  exhaust  action,  the  result  should  be  secured 
by  contracting  the  nozzle  and  not  by  contracting  the  choke. 

102.  Jets  Formed  by  a  Steady  Blast  of  Steam.— Figs.  113  to  115 
represent  jets  which  were  obtained  by  blocking  the  slide-valves  clear 
of  their  seats,  and  by  slightly  opening  the  throttle.  That  the  results 
thus  obtained  might  be  compared  with  those  presented  by  the  earlier 
figures,  the  throttle  was  so  adjusted  as  to  pass  similar  quantities  of 


222 


LOCOMOTIVE  PERFORMANCE. 


steam.  Thus,  with  the  locomotive  running  at  25  miles  per  hour  (Fig. 
107)  6090  pounds  of  steam  were  exhausted  each  hour.  The  steady 
blow  corresponding  is  represented  by  Fig.  113,  for  which  the  discharge 
equaled  6400  pounds  per  hour.  The  agreement  is  sufficiently  close  for 
practical  purposes. 

The  similarity  in  the  form  of  the  jets  serves  to  fully  explain  the 
success  of  the  "blow"  in  producing  draft.  A  critical  comparison  of 
these  jets  fails  to  disclose  any  important  difference,  except  in  the 


POUNDS  OF  STEAM   PER  HOU 


FIG.  113. 


FIG.  114. 


FIG.  115. 


character  of  the  curves  bounding  their  outline  and  in  that  of  the 
velocity  curves.  The  lines  in  the  jets  produced  by  blow  are  more 
sinuous  than  in  the  jets  which  are  sustained  by  exhaust  section.  Cor- 
responding measurements  of  the  draft  show  that  the  steady  jet  pos- 
sesses substantially  the  same  draft-producing  power  as  the  intermittent 
exhaust,  the  essential  factor  being  the  weight  of  steam  exhausted  in 

a  given  time. 

103.  The  Form  of  the  Jet  as  Influenced  by  Different  Tips.— 
At  the  time  when  the  Master  Mechanics'  Committee  made  its  investi- 


THE  FRONT  END. 


223 


gation  three  forms  of  tips  were  in  common  use.  These  are  designated 
as  X,  Y,  and  Z,  Fig.  119.  The  tip  X  ends  in  a  plain  cylindrical  portion 
2"  in  length;  the  tip  Y  is  contracted  in  the  form  of  a  frustrum  of  a 
cone;  and  the  tip  Z  is  in  the  form  of  a  plain  cylinder,  ending  in  an 
abrupt  cylindrical  contraction.  The  forms  of  the  jets  delivered  by 
these  tips  were  in  each  case  denned  by  methods  already  described.  It 
was  found  that  while  the  form  was  nearly  the  same  in  all  cases,  the 
jet  delivered  by  the  tip  X  has  the  least  divergence,  and  that  of  the  tip 


FIG.  116. 


FIG.  117 


FIG.  118. 


Z  the  greatest.  As  to  draft-producing  qualities,  the  committee  was 
unable  to  present  convincing  proof  in  favor  of  any  one  of  the  forms 
experimented  upon,  the  results  obtained  being  practically  identical. 
The  opinion  is  expressed,  however,  that  the  highest  efficiency  will  be 
obtained  from  the  jet  which  is  most  dense,  and  for  this  reason  they 
were  inclined  to  favor  the  form  X. 

104.  The  Form  and  Efficiency  of  the  Jet  as  Affected  by  Bars 
over  the  Tip. — It  is  well  known  that  engines  which  refuse  to  steam 
may  sometimes  be  made  to  do  so  by  bridging  the  exhaust-nozzle  with 


224 


LOCOMOTIVE  PERFORMANCE. 


a  small  piece  of  round  iron  or  by  a  bar  or  bars  having  a  knife-edged 
cross-section  .designed  to  spread  the  jet  and  at  the  same  time  impede 
its  motion  as  little  as  possible.  Experiments  were  therefore  made  by 
the  committee  of  1896,  both  upon  round  bars  and  upon  crosses,  shown 
by  Fig.  120,  with  results  confirming  the  experience  on  the  road.  The 
effect  of  such  a  bar  upon  the  form  of  the  jet  is  shown  by  Fig.  116,  it 
crowds  the  interior  portions  outward.  The  jet  is  not  made  materially 
larger,  but  the  curves  representing  different  velocities  are  crowded  close 
together  on  either  side .  As  to  the  effect  of  such  a  device  on  the  efficiency 
of  the  jet,  it  was  found  that  the  draft  was  improved,  but  in  all 
cases  the  presence  of  the  bridge  so  much  increased  the  back  pressure 
that  the  efficiency  of  the  front  end  was  reduced.  In  other  words,  the 
presence  of  the  bar  or  cross  produced  the  same  effect  upon  the  back 
pressure  as  the  substitution  of  a  smaller  nozzle  without  the  bars.  It 
was  found  that  cross-bars  (Fig.  120),  not  wider  than  f  of  an  inch,  and 
having  the  lower  portion  shaped  to  a  sharp  knife-edge,  placed  on 
the  nozzle,  or  any  distance  not  greater  than  one  inch  above  it, 
increased  the  back  pressure,  and  that  wider  bars  increased  the 
back  pressure  at  a  greater  distance  from  the  nozzle.  In  view  of  these 
facts,  and  also  in  view  of  the  fact  that  all  evidence  goes  to  show  that 
for  highest  efficiency  the  jet  should  be  kept  as  well  compacted  as  pos- 


FIG.  119. 

sible,  the  practice  of  splitting  it  up  was  not  commended.  It  is  believed 
to  be  better  practice  in  cases  where  the  draft  is  unsatisfactory  to  reduce 
the  diameter  of  the  exhaust-nozzle  than  to  attempt  to  secure  the  de- 
sired result  by  employing  a  larger  nozzle  with  a  bridge  above  it. 

105.  The  Form  of  the  Jet  as  Affected  by  Stack  Proportions. — 
It  has  already  been  suggested  that  the  jet  adapts  itself  to  the  proportions 
of  the  stack  through  which  it  discharges,  and  that  it  shows  a  disposition 
to  avoid  contact  with  the  sides  of  the  stack  until  very  near'  its  top. 
The  facts  in  the  case  are  better  and  more  definitely  defined  by  Fig. 
117,  which  shows  the  form  of  the  jet  in  the  presence  of  a  false  lining 
or  choke  in  the  stack,  so  proportioned  as  to  reduce  the  effective 
diameter  of  the  stack  from  16",  its  normal  size,  to  12".  It  is  evident 
that  the  presence  of  such  a  device  acts  as  a  throttle  on  the  delivery 
of  the  combined  stream  of  gases,  and  that  by  so  doing  it  produces  a  ma- 


THE  FRONT  END. 


225 


terial  reduction  in  the  velocity  of  the  current  within  the  smoke-box, 
or  points  immediately  about  the  jet  and  below  the  stack.  The  re- 
duced velocity  allows  the  stream  to  broaden  out,  but  it  narrows  again, 
and  doubtless  in  some  portions  of  its  cross-section  its  velocity  increases 
as  it  approaches  the  base  of  the  contracted  stack.  Fig.  118  may  be 
employed  as  a  convenient  reference  in  connection  with  the  two  pre- 
ceding figures. 


Bridge  J 


Bridge 


FIG.  120. 

106.  The  Jet  as  Affected  by  Cut-off. — For  the  purpose  of  deter- 
mining the  effect,  if  any,  upon  the  form  of  the  jet  of  changes  in  cut- 
off, the  load  at  the  locomotive  draw-bar  was  held  constant,  the  speed 
controlled  by  throttle-opening,  and  the  engine  run  with  the  reverse- 
lever  in  several  different  positions,  the  form  of  the  jet  being  deter- 
mined  meanwhile  by   methods   already   described.     The   conclusion 
drawn  from  these  tests  is  that  changes  in  the  cut-off  have  no  effect 
upon  the  form  and  character  of  jet,  except  in  so  far  as  they  affect  the 
quantity  of  steam  discharged. 

107.  The  Stack  Problem. — Prior  to  1902  experiments  under  service 
conditions  involving  front-end  appliances  were  but  little  concerned 
with   the   problems   of    the    stack.*     This  was   due    to   no  lack  of 
appreciation   of    the  importance    of   the   stack,   but   rather   to   the 
complicated  nature  of  the  problem,   and  to  the  fact  that  the  need 
of    information   concerning   other    details   had   been   more    urgent. 
Previous  to  this  time  it  frequently  happened  that  one  locomotive, 
having    twice    the  cylinder  power  and  boiler  capacity  of  another, 
would  be  fitted  with  a   stack  of  the  same  size.     In  this  case  the 
furnace  gases  and  exhaust  steam  of  the  larger  locomotive  were  re- 

*  A  few  years  ago  there  were  undertaken  at  Hanover,  Germany,  an  elaborate 
series  of  tests  designed  to  solve  the  stack  problem.  The  results,  which  in  this  country 
have  been  known  as  those  of  the  von  Borries-Troske  tests,  have  been  widely  pub- 
lished. They  were  conducted  upon  a  full-sized  model  front  end,  steam  being  sup- 
plied from  a  stationary  boiler,  and  air  in  imitation  of  the  smoke-box  gas  being  ad- 
mitted to  the  front  end  through  a  restricted  opening.  While  they  have  undoubtedly 
served  well  to  guide  the  practice  of  German  railways,  they  have  not  greatly  influenced 
that  of  our  own  country. 


226  LOCOMOTIVE  PERFORMANCE. 

quired  to  find  their  way  through  an  opening  which  appeared  to  be  not 
too  large  for  the  smaller  locomotive.  It  was,  in  fact,  the  practice  of 
some  of  the  important  roads  to  make  all  stacks  of  the  same  diameter, 
regardless  of  the  size  of  the  locomotive  upon  which  they  were  to  be 
used.  It  is  evident  that  in  such  cases  the  highest  efficiency  could  only 
result  from  a  chance  combination,  and  the  action  in  many  cases  was 
necessarily  far  from  satisfactory.  Moreover,  these  conditions  did  not 
prevail  from  choice,  but  rather  because  the  information  necessary  to 
guide  practice  along  more  logical  lines  was  not  available.  In  view  of 
these  facts,  the  American  Engineer  of  New  York  City,  as  represented 
by  Mr.  G.  M.  Basford,  its  editor,  having  secured  the  cooperation  of  a 
committee  of  representative  motive-power  officials,*  agreed  to  become 
a  patron  of  the  locomotive  laboratory  of  Purdue  University,  for  the 
purpose  of  securing  information  which  would  aid  in  the  logical  design 
of  such  apparatus. f 

1 08.  The  Plan  of  the  Tests,  as  outlined  by  the  laboratory,  involved 
the  recognition  of  the  following  variable  factors : 

(a)  Form  of  Stack. — With  reference  to  this  factor,  two  contours 
only  were  provided,  one  straight  and  one  tapered. 

(6)  Diameter  of  Stack. — Each  form  of  stack  was  developed  into  a 

*  This  committee  consists  of  Mr.  Robert  Quayle,  Chicago  &  Northwestern;  Mr. 
A.  W.  Gibbs,  Pennsylvania;  Mr.  G.  R.  Henderson,  Atchison,  Topeka  &  Santa  Fe; 
Mr.  F.  H.  Clark,  representing  Mr.  F.  A.  Delano,  Chicago,  Burlington  &  Quincy;  Mr. 
W.  H.  Marshall  and  Mr.  H.  F.  Ball,  Lake  Shore  &  Michigan  Southern;  Mr.  F.  M. 
Whyte,  representing  Mr.  A.  M.  Waitt,  New  York  Central  &  Hudson  River;  Mr.  W.  S. 
Morris,  Chesapeake  &  Ohio;  Mr.  C.  H.  Quereau,  Denver  &  Rio  Grande;  Mr.  C.  A. 
Seley,  Norfolk  &  Western;  Mr.  J.  E.  Sague,  American  Locomotive  Company;  Mr. 
E.  M.  Herr,  who  was  Assistant  Superintendent  of  Motive  Power  of  the  Chicago  & 
Northwestern  when  the  Master  Mechanics'  Association  tests  of  1896  were  made;  and 
Mr.  H.  H.  Vaughan,  who,  while  not  then  connected  with  a  railroad,  was  a  recognized 
authority  in  matters  of  locomotive  design. 

f  By  the  arrangement  which  was  entered  into,  it  was  agreed  that  the  University 
should  contribute  to  the  proposed  work,  the  equipment  of  its  locomotive-testing 
laboratory  and  such  portion  of  the  time  of  its  expert  staff  as  could  readily  be  made 
available;  also  that  the  "American  Engineer"  would  meet  the  cost  of  special  appara- 
tus, of  supplies  in  excess  of  those  usually  required  in  the  routine  work  of  the  labora- 
tory, and  of  such  additional  help  as  might  be  necessary.  The  committee  already 
referred  to  assisted  in  an  advisory  capacity. 

A  full  description  of  the  work  thus  organized  and  of  the  results  drawn  therefrom 
will  be  found  running  through  the  issues  of  the  American  Engineer  for  the  year 
1902.  The  work  was  carried  on  in  connection  with  the  University's  locomotive, 
"Schenectady  No.  2."  This  is  an  eight-wheeled  engine,  weighing  100,000  pounds, 
having  a  boiler  the  least  diameter  of  which  is  52  inches. 


THE  FRONT  END.  227 

series  of  different  diameters,  the  diameters  being  9f  inches,  llf  inches, 
13f  inches,  and  15f  inches  respectively.  The  dimensions  given  apply 
to  all  portions  of  the  straight  stacks  above  the  base,  and  to  the  least 
diameter  of  the  tapered  stacks.  These  diameters  were  chosen  because 
of  their  close  agreement  with  the  diameters  used  in  the  von  Borries- 
Troske  experiments. 

(c)  Height  of  Stack. — Each  of  the  eight  stacks  already  described 
was  made  in  five  sections,  the  upper  four  sections  each  being  10  inches 
in  height.     This  provision  made  it  possible  to  employ  either  of  the 
eight  stacks  in  heights  varying  from  16 J  inches  to  56 J  inches. 

(d)  Exhaust-nozzles. — It  was  not  expected  that  the  work  should 
involve  any  investigation  of  exhaust-pipes  or  nozzles,  this  phase  of  the 
draft-appliance  problem  having  been  covered  as  already  described. 
It  was  assumed,  however,  that  in  order  to  get  the  maximum  efficiency 
of  each  different  diameter  and  height  of  stack,  it  would  be  necessary 
to  provide  a  variable  height  of  pipe. 

(e)  Power  of  the  Locomotive. — In  the  early  discussion  of  the  matter 
the  question  arose  as  to  whether  a  combination  of  apparatus,  which 
would  give  the  highest  efficiency  when  the  engine  was  worked  at  light 
power,  would  prove  the  most  efficient  under  conditions  of  heavy  power, 
and  that  there  might  be  no  question  arising  from  this  source  it  was 
determined  to  make  tests  under  each  combination  of  apparatus,  with 
the  engine  running  at  three  different  rates  of  power.     It  was  deter- 
mined, also,  that  this  could  best  be  accomplished  by  running  all  tests 
under  a  constant  steam  pressure,  a  fixed  cut-off,  and  a  .wide-open 
throttle,  the  desired  variations  of  power  being  obtained  by  varying  the 
speed.     The  conditions  chosen  were  approximately  as  follows:   Steam 
pressure,    180   Ibs.;    cut-off,  one-third    stroke;    speeds    for   different 
power,  20,  30,  and  40  miles   respectively;    the  power  under   these 
conditions  being  approximately  260,  370,  and  475.     The  amount  of 
steam  generated  by  the  boiler,  and  discharged  from  the  exhaust-tip, 
varies  nearly  in  direct  proportion  to  variations  in  power. 

109.  Conditions  at  the  Grate. — It  is  well  known  that  the  draft,  as 
measured  by  a  reduction  of  pressure  within  the  front  end,  is  affected 
by  conditions  other  than  those  which  control  the  action  of  the  steam- 
jet.  With  the  force  of  the  jet  remaining  constant,  the  draft  will  vary 
with  every  change  in  furnace  condition  which  serves  in  any  way  to 
affect  the  freedom  with  which  the  air  is  permitted  to  move  through  the 
grate  and  fire-box.  Thus,  all  other  things  remaining  constant,  the 
draft  is  reduced  by  opening  the  fire-door,  and  increased  by  closing  the 


228 


LOCOMOTIVE  PERFORMANCE. 


ash-pan  dampers.  Similarly,  a  thin,  clean  fire,  which  offers  but  little 
resistance  to  the  passage  of  air,  results  in  light  draft,  while  a  thick, 
heavy  fire,  which  impedes  the  movement  of  air  at  the  grate,  increases 
the  draft.  This  being  true,  it  was  deemed  essential  to  provide  for 
constant  conditions  at  the  grate.  As  this  could  not  be  done  in 
connection  with  solid  fuels,  the  experimental  engine  was  equipped 
for  burning  oil,  and  the  air-openings  into  the  fire-box  so  arranged 
that  they  would  at  all  times  be  of  fixed  dimensions.  The  degree  of 
ease,  therefore,  with  which  air  found  its  way  into  the  furnace  was 


FIG.  121. 

unaffected  by  the   condition  of  fire.     Sections  of  the  fire-box  as 
arranged  for  the  tests  are  shown  by  Fig.  121. 

no.  The  Experimental  Stacks  and  Nozzles. — The  stacks  em- 
ployed in  the  experiments  are  shown  by  Fig.  122.  Each  stack  was 
made  in  sections,  by  the  successive  removal  of  which  any  desired 
length  within  the  limits  shown  could  be  obtained.  The  several  sec- 
tions were  turned  to  fit  one  another  and  were  held  together  by  bolts 
acting  upon  outside  lugs.  The  nozzles  used  in  connection  with  the 
different  stacks  are  shown  by  Fig.  123,  and  the  details  of  their  con- 
struction by  Fig.  124.  When  in  use  the  nozzles  were  fixed  upon  a 
short  exhaust-pipe,  designed  in  accord  with  the  recommendation  of 
the  Master  Mechanics'  Committee.  They  consisted  of  a  wrought-iron 
body,  mounted  on  a  cast-iron  base,  and  fitted  at  the  top  with  a  suit- 


THE  FRONT  END. 


229 


able   tip.    All   had   the   same   diameter  of   tip,  namely,  4J  inches. 
Notation,  in  connection  with  stacks  and  nozzles,  was  employed  as  set 


No.3 


1-D 


1-C 


DIMENSIONS  OF  STACKS 


FIG.  122. 

forth  by  Figs.  122  and  123.     A  No.  7  stack  is  a  straight  stack  15| 
inches  in  diameter.     A  No.  7  A  stack   is  a  stack  26^  inches  long, 


rUi-^L-ii 


4     I 

g        J*          U 

&     s£ 

1      !      i 

-L     .i 

Q 

N?           •       ;£                      I 

Oik 

- 

i     r 

BmL 

1          ?          * 
f 

J                          ' 

-i-f 

0 

1 

H-- 

> 

Unto 

No.  7  ,    No.  6    No.  5     No.  4     No.  3     No.  2     No.  1 

FIG.  123. 

while  a  No.  7  D  stack  is  a  stack  56^  inches  long.     Similarly,  a  No. 
8  A  is  a  taper  stack  15f  inches  in  diameter  at  the  choke,  and  26 %  inches 


230 


LOCOMOTIVE  PERFORMANCE. 


long.  The  exhaust-pipes  and  nozzles  were  numbered.  Thus,  No.  1 
pipe  or  nozzle  is  5  inches  high  upon  a  10-inch  base,  while  nozzle  No.  7 
is  35  inches  high  upon  a  10-inch  base.  While  these  will  hereafter  be 


FIG.  124. 


referred  to  as  nozzles>  they  really  combine  in  one  design  a  pipe  and 
nozzle,  as  will  be  seen  by  the  drawing  representing  their  construc- 
tion, Fig.  124.  All  nozzles  were  used  upon  the  same  base  which, 
as  shown,  was  10  inches  in  height. 


THE  FRONT  END.  231 

in.  The  Tests.—  The  conditions  under  which  tests  were  made 
may  be  summarized  as  follows  : 

VASLABLE  SPEED  SERIES. 

Constants.  Variables. 

Boiler  pressure,  180.  }      g       dg:  2Q  3Q  ^  5  } 

23.8 


VARIABLE  CUT-OFF  SERIES. 

Constants.  Variables. 

Boiler  pressure,  180.  ~| 

Throttle,  wide  open.  ',       Cut-off,  per  cent  of  stroke, 

Speed,  40  miles  per  hour.  19,  23.8,  26.9,  and  35. 

194  revolutions  per  min.  J 

With  the  exception  of  certain  conditions,  which  could  be  omitted 
without  interfering  with  the  value  of  a  series,  tests  were  run  under  each 
condition  specified  above  for  each  of  40  different  stacks  and  these 
again  were  repeated  for  from  two  to  seven  different  heights  of  exhaust- 
pipes.  To  these  conditions  must  also  be  added  others  applying  to  an 
inside  or  sliding-stack,  the  results  of  which  will  be  separately  consid- 
ered. The  work  as  carried  out  involved  1032  distinct  tests,  for 
each  of  which  the  locomotive  was  brought  under  specific  conditions  of 
running,  and  for  each  of  which  a  considerable  series  of  observations 
were  made  of  permanent  record.  Besides  these  recorded  tests  there 
have  been  many  other  trial  or  rejected  tests. 

In  anticipation  of  a  series  of  tests,  the  engine  was  warmed  by  pre- 
liminary running.  It  was  then  started  for  a  test,  and  after  the  throttle 
and  reverse-lever  had  been  brought  to  their  desired  positions,  the  speed 
of  the  engine  was  made  to  vary  by  changing  its  load.  When  the  speed 
and  steam  pressure  were  both  that  which  were  required,  the  signal 
was  given  and  observations  were  taken.  The  engine  was  then  stopped, 
and  such  changes  in  stack  or  nozzle  were  made  as  were  necessary  for" 
the  next  set  of  observations,  after  which  the  process  above  described 
was  repeated.  In  this  manner  a  day's  work  consisted  in  a  succession 
of  short  runs,  with  intervals  between  to  allow  the  change  of  equipment. 

112.  Results.  —  A  detailed  statement  of  numerical  results,  obtained 
at  a  speed  of  40  miles  per  hour  under  a  cut-off  of  27  per  cent,  is  given  in 
Table  LIV  While  similar  tables  were  developed  under  the  same  cut- 
off for  speeds  of  20,  30,  50,  and  60  miles  per  hour  and  under  a  constant 
speed  of  40  miles  per  hour,  under  several  different  cut-offs,  it  appears 


232  LOCOMOTIVE  PERFORMANCE 

unnecessary  to  transfer  to  these  pages  the  whole  of  so  voluminous  a 
record.* 

1 13.  A  Basis  of  Comparison. — A  careful  study  of  all  results  made 
clear  the  fact  that  the  relative  value  of  the  various  devices  tested  could 
properly  be  determined  by  comparing  the  draft  values  resulting  from 
their  use.  That  is,  that  the  best  stack  was  that  which,  under  given 
conditions,  gave  the  best  draft.  Similarly,  that  the  best  height  of 
nozzle  was  assumed  to  be  that  which  gave  the  best  draft.  This  state\ 
ment  ignores  the  whole  question  of  back  pressure,  but  in  the  work 
described  this  is  justified,  because  of  the  fact  that  the  changes  made 
as  the  experiments  progressed  were  found  to  produce  no  measur- 
able effect  upon  the  back  pressure.  While,  therefore,  in  Table  LIV. 
values  are  given  for  both  back  pressure  and  efficiency,  the  compari- 
sons which  follow  are  concerned  only  with  the  draft,  f 

*  The  full  record  will  be  found  in  pages  of  the  American  Engineer  and  Railroad 
Journal,  to  which  references  have  previously  been  made. 

f  In  outlining  the  tests  it  was  proposed  to  base  all  comparisons  upon  the  effi- 
ciency of  the  jet,  and  efficiency  was  defined  as  the  ratio  of  back  pressure  to  draft. 
The  assumption  of  such  a  measure  is  based  upon  the  fact  that  the  result  which  is  sought 
by  the  use  of  any  combination  of  draft  appliances  is  a  reduction  of  pressure  within  the 
front  end,  and  that  the  force  effecting  such  a  reduction  of  pressure  is  a  function  of  the 
pressure  of  steam  in  the  passage  between  the  cylinders  and  the  exhaust- tip.  The 
maintenance  of  considerable  pressures  in  the  exhaust-passages  tends  to  reduce  the 
economic  performance  of  the  engine,  hence  it  is  desired  that  the  necessity  for  such 
pressures  be,  so  far  as  practicable,  avoided.  The  proposed  measure  of  efficiency  takes 
all  this  into  account,  for  by  its  use  that  arrangement  of  apparatus  which  will 
give  a  desired  reduction  of  pressure  in  the  front  end  in  return  for  the  least  back  pres- 
sure will  be  the  most  efficient.  Such  a  conception  is  perfectly  logical.  It  is  not  new, 
but  on  the  contrary  is  one  which  has  been  many  times  employed  in  the  study  of  draft 
appliances. 

The  preceding  statement  is  general  in  its  application.  It  applies  not  only  to 
the  tests  under  consideration  but  to  all  tests  which  may  be  made  for  the  pur- 
pose of  determining  the  value  of  this  or  that  draft  appliance.  It  happens,  how- 
ever, that  in  the  experiments  under  consideration,  the  exhaust- tip  was  of  the 
same  size  for  all  tests.  Furthermore,  it  appears  as  one  of  the  significant  results 
obtained  from  the  tests,  that  a  change  in  the  height  of  the  exhaust-pipe  does 
not  affect  the  back  pressure  by  a  measurable  amount.  Consequently,  so  far  as 
the  present  study  is  concerned,  the  back  pressure  for  any  given  condition  of  run- 
ning appears  as  a  constant;  and  the  efficiency  which,  in  the  general  case,  is  a  func- 
tion of  both  back  pressure  and  draft,  is  left  to  depend  upon  draft  alone.  All  this 
being  true,  it  appears  that  effects  resulting  from  changes  in  the  front-end  mechan- 
ism, such  as  were  involved  by  the  experiments  under  consideration,  are  quite  as 
well  shown  by  a  direct  comparison  of  draft  values  as  by  a  comparison  of  efficiency 
values.  Moreover,  the  draft  values  involve  a  single  observation  made  under  condi- 


THE  FRONT  END. 


233 


TABLE  LIV. 
FORTY-MILE  SERIES. 


CONSTANTS. 


Pounds  of  Steam  used. 


Cut-off. 


f  Miles  per  hour 40 

\R.  P.  M. 194.4 

f  Per  hour 12988 

\  Per  minute 216 

f  in  inches 6.4 

\  in  per  cent  of  stroke        26.9 


M.E.P.  52.0  los 

RESULTS. 


Smoke-box 

Smoke-box 

Pressure. 

Pressure. 

y 

*o  ^  > 

, 

>' 

».1 

1. 

. 

'« 

$* 

fj 

fl 
0) 

£ 

£•?« 

»li 

•d 

1 

n 

K 

%£* 
§m" 

w 

M 

§3 

0  0 

fe 

3 

•a 
m 

3 

i 

jpSl 

0 

|i 

o 
W 

I. 

II. 

III. 

IV. 

V. 

VI. 

I. 

ii. 

III. 

IV. 

V. 

VI. 

1 

2.7 

.2 

.043 

.016 

i 

2.65  ' 

.4 

.05 

.018 

2 

2.24 

.2 

.0432 

.019 

2 

2.23 

.4 

.0504 

.023 

3 

3 

2.52 

.4 

.0503 

.02 

Base 

4 

2.25 

.3 

.0468 

.021 

1-C 

4 

2.05 

.7 

.0612 

.03 

No.  1 

5 

2.25 

.2 

.0432 

.019 

5 

2.13 

.8 

.0648 

.03 

6 

2.4 

.2 

.0432 

.018 

6 

2.2 

.9 

.0684 

.031 

7 

2.55 

.0 

.036 

.014 

7 

2.4 

2.0 

.072 

.03 

1 

2.3 

.2 

.043 

.019 

1 

2.45 

1.3 

.047 

.019 

2 

2.25 

.4 

.0504 

.022 

2 

2.25 

1.4 

.0504 

.022 

3 

2.50 

.6 

.0577 

.023 

3 

2.4 

1.4 

.0503 

.021 

1-A 

4 

2.3 

.7 

.061 

.027 

1-D 

4 

2.3 

1.8 

.0648 

.028 

5 

2.22 

1.7 

.0612 

.028 

5 

2.22 

1.9 

.0684 

.031 

6 

2.2 

1.7 

.0612 

.028 

6 

2.2 

2.0 

.072 

.033 

7 

2.45 

1.5 

.054 

.022 

7 

2.3 

2.1 

.0756 

.033 

1 

2.2 

.4 

.05 

.023 

1 

2.6 

2.3 

.083 

.032 

2 

2.3 

.4 

.0504 

.022 

2 

2.27 

2.4 

.0864 

.038 

3 

2.35 

.4 

.0503 

.021 

3 

2.35 

2.6 

.0936 

.04 

1-B 

4 

2.25 

.8 

.065 

.029 

2-A 

4 

2.0 

2.4 

.0864 

.043 

5 

2.21 

.9 

.0684 

.031 

5 

2.21 

2.2 

.0792 

.036 

6 

2.4 

.9 

.0684 

.028 

6 

2.4 

2.0 

.072 

.03 

7 

2.25 

.9 

.0684 

.03 

7 

2.45 

1.6 

.0578 

.024 

234 


LOCOMOTIVE  PERFORMANCE. 


TABLE  LIV. — (Continued). 
FORTY-MILE   SERIES. 


Smoke-box 

Smoke-box 

Pressure. 

Pressure. 

Jb 

,,     ^ 

L 

>> 

kg 

-      1 

i 

1 

1 

||l 

hi 
III 

z$ 
11 

0 

a 
.2 
g 

£ 

•jj 

6 
1 

III 

"fe£ 

111 

l! 

e 
p 

02 

ft 

o 

£ 

w 

02 

fc 

O 

n 

£ 

W 

I. 

II. 

III. 

IV. 

V. 

VI. 

I. 

II. 

III. 

IV. 

V. 

VI. 

1 

2.4 

3.1 

.111 

.046 

1 

2.5 

2.7 

.097 

.038 

2 

2.2 

3.2 

.1152 

.052 

2 

2.27 

2.8 

.1008 

.044 

3 

2.37 

3.3 

.1188 

.05 

3 

2.34 

2.7 

.097 

.045 

4 

2.2 

3.0 

.108 

.049 

3-C 

4 

2.3 

3.1 

.112 

.049 

2-B 

5 

2.25 

2.9 

.1044 

.046 

5 

2.23 

3.1 

.112 

.05 

6 

2.4 

2.5 

.09 

.037 

6 

2.3 

3.0 

.108 

.047 

7 

2.4 

2.2 

.0792 

.033 

.    7 

2.4 

2.8 

.101 

.042 

1 

2.45 

3.5 

.126 

.051 

1 

2.6 

2.4 

.086 

.033 

2 

2.15 

3.8 

.1368 

.064 

2 

2.23 

2.7 

.0972 

.044 

3 

2.38 

3.7 

.1332 

.056 

3 

2.6 

3.0 

.108 

.041 

2-C 

4 

2.3 

3.5 

.126 

.055 

3-D 

4 

2.4 

3.0 

.108 

.045 

5 

2.25 

3.5 

.126 

.056 

5 

2.2 

3.0 

.108 

.049 

6 

2.2 

3.1 

.1116 

.051 

6 

2.2 

3.1 

.112 

.051 

7 

2.2 

2.7 

.0972 

.044 

7 

2.4 

3.2 

.115 

.048 

1 

2.45 

4.0 

.144 

.059 

1 

2.3 

3.0 

.108 

.047 

2 

2.1 

4.3 

.1548 

.074 

2 

2.3 

3.3 

.1188 

.052 

3 

2.42 

4.0 

.144 

.059 

3 

2.35 

3.0 

.108 

.046 

2-D 

4 

2.4 

3.9 

.1404 

.058 

4-A 

4 

2.2 

2.9 

.104 

.047 

5 

2.21 

4.0 

.144 

.065 

5 

2.3 

2.5 

.09 

.039 

6 

2.4 

3.4 

.122 

.051 

6 

2.2 

2.0 

.072 

.033 

7 

2.25 

3.2 

.1152 

.051 

7 

2.4 

1.4 

.05 

.021 

1 

1 

2.2 

3.5 

.126 

.057 

2 

2.33 

2.1 

.0756 

.032 

2 

2.35 

4.1 

.1476 

.063 

3 

3 

2.34 

3.4 

.122 

.052 

Base 

4 

2.3 

1.9 

.068 

.030 

4-B 

4 

2.25 

3.6 

.130 

.058 

No.  2 

5 

2.22 

1.6 

.058 

.026 

5 

2.27 

3.2 

.152 

.051 

6 

2.2 

1.2 

.043 

.019 

6 

2.4 

2.7 

.097 

.041 

7 

2.5 

.9 

.032 

.013 

7 

2.6 

2.1 

.076 

.029 

1 

2.6 

2.3 

.082 

.032 

1 

2.5 

4.3 

.155 

.062 

2 

2.4 

2.6 

.094 

.039 

2 

2.3 

4.6 

.1656 

.072 

3 

2.4 

2.65 

.096 

.039 

3 

2.28 

4.0 

.144 

.063 

3-A 

4 

2.2 

2.6 

.094 

.043 

4-C 

4 

2.3 

4.0 

.144 

.063 

5 

2.23 

2.4 

.086 

.038 

5 

2.34 

3.7 

.133 

.057 

6 

2.2' 

2.1 

.076 

.034 

6 

2.4 

3.0 

.108 

.045 

7 

2.5 

1.7 

.061 

.025 

7 

2.3 

2.6 

.094 

.041 

1 

2.5 

2.7 

.097 

.039 

1 

2.8 

5.3 

.191 

.068 

2 

2.3 

•2.6 

.094 

.041 

2 

2.27 

5.0 

.18 

.079 

3 

2.5 

2.9 

.104 

.042 

3 

2.41 

4.4 

.158 

.065 

3-B 

4 

2.3 

2.9 

.104 

.045 

4-D 

4 

2.4 

4.3 

.155 

.065 

5 

2.25 

2.9 

.104 

.046 

5 

2.4 

4.2 

.151 

.063 

6 

2.2 

2.6 

.094 

.043 

6 

2.4 

3.8 

.136 

.057 

7 

2.65 

2.4 

.087 

.033 

7 

2.35 

3.2 

.115 

.049 

THE  FRONT  END. 


235 


TABLE  LIV.— (Continued}. 
FORTY-MILE  SERIES. 


Smoke-box 

Smoke-box 

Pressure. 

Pressure. 

i 

, 

^  . 

.1   , 

1 

QQ 

Nozzle. 

Observed 
Back  Pre 
sure,  Lbs 

Inches  of 
Water 
Observed 

Pounds  Ca 
culated. 

Efficiency. 

1 

GQ 

Nozzle. 

V  03 

•s<6;3 

£3  of 

jdg 

0 

Inches  of 
Water 
Observed 

Pounds  Ca 
culated. 

Efficiency. 

I. 

II. 

III. 

IV. 

V. 

VI. 

I. 

II. 

III. 

IV. 

V. 

VI. 

1 

1 

2.27 

4.0 

.144 

.064 

2 

2.35 

2.8 

.1008 

.043 

2 

2.33 

4.2 

.151 

.065 

3 

3 

2.2 

4.2 

.151 

.068 

Base 

4 

2.45 

1.9 

.0684 

.028 

6-B 

4 

2.3 

3.4 

.1224 

.053 

No.  3 

5 

5 

2.24 

3.0 

.108 

.048 

6 

2.45 

1.1 

.0396 

.016 

6 

2.15 

2.4 

.086 

.040 

7 

2.25 

.7 

.0252 

.011 

7 

2.25 

1.9 

.0684 

.030 

1 

2.41 

3.2 

.115 

.048 

1 

2.1 

4.4 

.158 

.075 

2 

2.33 

3.5 

.126 

.054 

2 

2.26 

4.6 

.1656 

.073 

3 

2.4 

3.1 

.1116 

.046 

3 

2.2 

4.5 

.162 

.074 

5-A 

4 

2.4 

2.8 

.1008 

.042 

6-C 

4 

2.35 

3.9 

.1404 

.06 

5 

2.25 

2.4 

.0864 

.038 

5 

2.27 

3.4 

.1224 

.056 

6 

2.2 

2.0 

.072 

.033 

6 

2.2 

2.9 

.104 

.047 

7 

2.35 

1.4 

.0503 

.021 

7 

2.25 

2.4 

.0684 

.038 

1 

2.37 

3.2 

.115 

.049 

1 

2.1 

4.8 

.173 

.082 

2 

2.4 

3.9 

.1402 

.058 

2 

2.25 

5.0 

.18 

.08 

3 

2.36 

3.4 

.1221 

.052 

3 

2.3 

5.2 

.1872 

.081 

5-B 

4 

2.45 

3.2 

.1152 

.047 

6-D 

4 

2.4 

4.4 

.1584 

.066 

5 

2.25 

3.2 

.1152 

.051 

5 

2.2 

4.1 

.1476 

.067 

6 

2.3 

2.8 

.1008 

.044 

6 

2.25 

3.3 

.1188 

.053 

7 

2.4 

2.8 

.0792 

.033 

7 

2.5 

2.8 

.1008 

.04 

1 

2.3 

3.2 

.115 

.05 

1 

2 

2.25 

3.6 

.1296 

.058 

2 

2.30 

2.8 

.1 

.043 

3 

2.4 

3.6 

.130 

.054 

3 

5-C 

4 

2.4 

3.7 

.1332 

.055 

Base 

4 

2.3 

1.7 

.061 

.027 

5 

2.25 

3.6 

.1296 

.057 

No.  4 

5 

6 

2.25 

3.4 

.122 

.054 

6 

2.3 

.75 

.027 

.012 

7 

2.4 

3.1 

.1116 

.046 

7 

2.35 

.5 

.018 

.008 

1 

2.45 

3.4 

.122 

.05 

1 

2.22 

3.4 

.122 

.055 

2 

2.26 

3.8 

.1368 

.059 

2 

2.35 

3.6 

.129 

.055 

3 

2.3 

3.6 

.13 

.056 

3 

2.13 

3.0 

.108 

.051 

5-D 

4 

2.45 

4.0 

.144 

.054 

7-A 

4 

2.33 

2.7 

.097 

.042 

5 

2.22 

3.9 

.1404 

.063 

5 

2.25 

2.4 

.086 

.038 

6 

2.3 

3.8 

.1368 

.059 

6 

2.3 

1.6 

.057 

.025 

7 

2.35 

3.5 

.126 

.054 

7 

2.3 

1.1 

.039 

.017 

1 

2.4 

3,6 

.129 

.054 

1 

2.18 

3.6 

.129 

.059 

2 

2.3 

3.5 

.126 

.055 

2 

2.25 

4.2 

.158 

.07 

3 

2.2 

3.4 

.122 

.055 

3 

2.30 

3.6 

.130 

.056 

6-A 

4 

2.45 

2.7 

.0972 

.04 

7-B 

4 

2.4 

3.4 

.122 

.051 

5 

2.28 

2.4 

.0864 

.036 

5 

2.22 

3.0 

.108 

.049 

6 

2.4 

1.8 

.0648 

.027 

6 

2.2 

2.4 

.086 

.039 

7 

2.4 

1.3 

.0468 

.019 

7 

2.2 

1.9 

.068 

.031 

236 


LOCOMOTIVE  PERFORMANCE 

TABLE  LIV.— (Continued). 

FORTY-MILE  SERIES. 


Smoke-box 

Smoke  -box 

Pressure. 

Pressure. 

£  " 

"e8 

0)  03 

•t 

1^ 

*g  fe  B 

°i 

g 

T3Pn  J 

**"      > 

OT? 

?? 

1 

Nozzle. 

jit 

|£o 

os.2 

V 

S 

0> 

1 

W 

44 

1 

0) 

1 

o 

hu 

Jdg 

0 

|ll 

Pounds 
culate 

Efficien< 

I. 

II. 

III. 

IV. 

V. 

VI. 

I. 

II. 

III. 

IV. 

V. 

VI. 

1 

2.21 

3.6 

.129 

.058 

1 

2.4 

4.9 

.176 

.073 

2 

2.35 

4.6 

.166 

.071 

2 

2.23 

4.7 

.169 

.075 

3 

2.37 

4.0 

.144 

.061 

3 

2.4 

4.2 

.151 

.069 

7-C 

4 

2.35 

3.8 

.136 

.058 

8-D 

4 

2.4 

3.6 

.130 

.054 

5 

2.22 

3.8 

.136 

.062 

5 

2.8 

3.6 

.129 

.036 

6 

2.3 

3.2 

.1156 

.05 

6 

2.4 

2.7 

.097 

.04 

7 

2.45 

2.9 

.104 

.043 

7 

2.25 

2.3 

.082 

.036 

1 

2.21 

3.9 

.14 

.067 

Nor- 

2 

2.4 

4.7 

.169 

.070 

mal, 

3 

2.3 

4.2 

.151 

.066 

Petti- 

7-D 

4 

2.2 

4.2 

.151 

.069 

coat 

5 

2.25 

4.2 

.151 

.067 

Pipe 

6 

2.35 

3.7 

.133 

.057 

In 

* 

2.4 

3.9 

.14 

.058 

7 

2  35 

3  5 

126 

054 

Nor 

1 

2.22 

3.5 

.126 

.057 

mal, 

2 

2.3 

3.6 

.129 

.056 

Petti- 

3 

2.4 

3.0 

.108 

.045 

coat 

8-A 

4' 

2.35 

2.3 

.082 

.035 

Pipe 

5 

2.33 

1.9 

.068 

.029 

Out 

* 

2.4 

3.8 

.136 

.057 

Q 

9     QA 

1  25 

045 

02 

7 

2.35 

.9 

.032 

.014 

Slid- 

1 
2 

2.8 
2  2 

3.6 

Q     A 

.129 
108 

.046 

OJ.Q 

1 

2.25 

4.1 

.148 

.066 

ing  A 

3 

2.3 

2.7 

.097 

.042 

9 

9   A 

4  2 

A«O 

8-B 

3 
4 

2  45 
2.35 

3.5 

2.9 

.126 
.104 

.051 
.045 

Slid- 

1 
2 

2.6 
2.2 

3.0 
3.4 

.108 
.122 

.041 
.055 

5 

2.5 

2.4 

.086 

.035 

ing  B 

3 

2.3 

3.1 

.111 

.048 

« 

2  4 

1  9 

068 

028 

7 

2.25 

1.4 

.05 

.022 

1 

2.6 

3.5 

.126 

.048 

OllCl" 

2 

2  3 

Q  q 

140 

AA1 

1 

1.27 

4.5 

.162 

.071 

ing  C 

3 

2^5 

4.2 

.151 

.06 

9 

2    OK 

4  4 

158 

07 

3 

2.4 

4.0 

.144 

.06 

1 

2.4 

4.0 

.144 

.06 

8-C 

4 

2.25 

3.4 

.122 

.054 

.       " 

2 

2.2 

4.1 

.147 

.067 

5 

2.7 

3.0 

.108 

.037 

ing  -U 

3 

2.4 

4.0 

.144 

.06 

6 

2.4 

2.4 

.086 

.036 

7 

2.2 

1.9 

.068 

.031 

*  Normal. 


THE  FRONT  END. 


237 


114.  The  Effect  upon  Stack  Proportions  of  Changes  in  Speed 
and  Cut-off. — The  experiments  were  made  to  involve  a  great  variety 
of  conditions  with  reference  to  speed  and  cut-off,  in  order  that  the 
differences  in  the  efficiency  of  the  stack  arrangement,  which  resulted 
from  such  changes,  might  be  known.  From  a  careful  study  of  all  of  this 
data  it  can  be  stated  with  confidence  that,  within  reasonable  limits, 
no  change  in  the  condition  of  running  affects  in  any  marked  degree  the 
efficiency  of  the  stack;  that  a  stack  and  nozzle  which  are  satisfactory  at 


Stack  A 


Height  26!^ 


Stack  B 


Height  36 'j 


Stack  Diameter.   Inches 


FIG.   125. — Straight  Stack, 
Nozzle  No.  2. 


Stack  Diameter.   Inches 


FIG.  126.— Straight  Stack, 
Nozzle  No.  2. 


one  speed  will  be  found  satisfactory  at  all  speeds,  and  if  satisfactory 
under  one  condition  of  cut-off  they  will  be  found  reasonably  satisfactory 
under  all  conditions  of  cut-off.  This  conclusion,  which  is  of  the  high- 
est importance,  cannot  be  perfectly  demonstrated  without  the  use  of 
an  elaborate  display  of  data,  but  its  truth  is  well  illustrated  by  the 
similarity  of  the  curves  representing  the  draft  obtained  under  three 
different  speeds  by  means  of  several  different  stacks,  Figs.  125  to  132.* 

tions  favorable  to  accuracy,  and,  consequently,  they  supply  a  better  basis  for  compari- 
son than  efficiency,  which  depends  on  two  observations,  one  of  which  is  rather  difficult 
to  obtain. 

*  These  figures  have  been  chosen  to  illustrate  the  effect  upon  the  draft  of  changes 
in  the  proportions  of  the  stack  and  height  of  the  nozzle.  Figs.  125  to  128  present 
results  obtained  by  using  straight  stacks  of  various  heights  and  diameters,  in  connec- 
tion with  an  exhaust  tip  2  inches  below  the  center  of  the  boiler  Figs.  129  to  132 
show  results  obtained  by  the  use  of  tapered  stacks  and  an  exhaust  tip  20  inches  above 
the  center  of  the  boiler.  The  steam  pressure,  throttle  opening,  and  cut-off  were  the 
same  for  all  tests  represented  by  these  diagrams. 


238 


LOCOMOTIVE  PERFORMANCE. 


Curves  representing  results  obtained  at  different  cut-offs  present  the 
same  characteristics.    With  a   given  weight  of  steam  discharged, 


Stack  C 


Height  43 '4 


Height  56Vfc 


Stack  Diameter.  Inches 

FIG.  127.— Straight  Stack, 
Nozzle  No.  2. 


Stack  Diameter.   Inches 


FIG.  128.— Straight  Stack, 
Nozzle  No.  2. 


whether  in  the  heavy  exhausts  incident  to  slow  speed,  or  the  more 
rapid  impulses  which  are  sent  forth  at  higher  speed,  the  draft  result- 
stack  A  Height  26 vg  StackB  Height  36% 


0  M.P  H 


11 '4 


13V 


Stack  Diameter.   Inches 

FIG.  129.— Tapered  Stack, 
Nozzle  No.  7. 


Stack  Diameter.    Inches 

FIG.  130.— Tapered  Stack, 
Nozzle  No.  7. 


ing  is  practically  the  same.  But  whenever  the  weight  of  steam  dis- 
charged per  minute  changes,  the  draft  will  change.  That  this  is  true 
for  changes  of  speed  is  made  clear  by  Table  LV.,  in  which  is  given  a 


THE  FRONT  END. 


239 


comparison  of  changes  in  draft  values  with  corresponding   changes 
in  the  volume  of  steam  exhausted. 


Stack  C 


Height 


Stack  D 


Height  5GJ4 


Stack  Diameter.    Inches 


FIG.  131.— Tapered  Stack, 
Nozzle  No.  7. 


Stack  Diameter.   Inches 


FIG.  132.— Tapered  Stack, 
Nozzle  No.  7. 


TABLE  LV. 

A  COMPARISON  OF  CHANGES  IN   DRAFT  VALUES    WITH  CORRESPOND- 
ING   CHANGES   IN  THE  VOLUME   OF   STEAM   EXHAUSTED. 

Nozzle  No.  3.     Exhaust-tip  on  Center  Line  of  Boiler. 


Stacks. 

Change  in 

Ratio  of 

Ratio  of 

Speed, 
Miles. 

Change  in 
Draft. 

Change  in 
Steam  Used 

Height. 

Diameter. 

Form. 

per  Hour. 

864 

® 

Taper 

20  to  30 

.25 

.33 

26^ 

Q 

Taper 

30  to  40 

.30 

.19 

36  1 

9- 

Taper 

20  to  30 

.30 

.33 

36, 

9j 

Taper 

30  to  40 

.23 

.19 

4ft 

9i 

Taper 

20  to  30 

.15 

.33 

46^ 

9i 

Taper 

30  to  40 

.19 

.19 

5ft 

9i 

Taper 

20  to  30 

.25 

.33 

56^ 

9i 

Taper 

30  to  40 

.14 

.19 

2ft 

Hi 

Taper 

20  to  30 

.23 

.33 

2ft 

• 

Hi 

Taper 

30  to  40 

.14 

.19 

36, 

• 

Hi 

Taper 

20  to  30 

.29 

.33 

36i 

• 

Hi 

Taper 

30  to  40 

.13 

.19 

4ft 

Hi 

Taper 

20  to  30 

.24 

.33 

4ft 

n\ 

Taper 

30  to  40 

.11 

.19 

^ 

Hi 

Taper 

20  to  30 

.26 

.33 

oft 

Hi 

Taper 

30  to  40 

.15 

.19 

Average.  .  . 

.21 

.26 

Following  the  first  line  of  this  table,  it  will  be  seen  that  when  the 
speed  is  changed  from  20  to  30  miles,  the  draft  is  increased  in  the  ratio 


240 


LOCOMOTIVE  PERFORMANCE. 


of  from  1  to  1.25,  and  the  steam  exhausted  is  increased  in  the  ratio  of 
from  1  to  1 .33,  which  is  an  approach  to  agreement.  Similar  comparisons 
are  shown  for  various  diameters  and  heights  of  stacks,  the  average  of  all 
being,  for  changes  in  draft,  1.21,  and  for  changes  in  steam  exhausted, 
1.26,  which  makes  the  check  very  close.  The  result  of  comparisons  in- 
volving other  values  tends  to  further  confirm  the  general  conclusion. 
115.  A  Review  of  Best  Results. — From  an  inspection  of  the  re- 
sults of  all  the  tests,  the  highest  draft  readings  have  been  selected  for 
each  condition  of  speed  and  cut-off.  These,  with  the  designation  of 
stacks  and  nozzle  employed  in  securing  them,  are  set  down  in  the 
columns  of  Table  LVI.  Results  thus  chosen  constitute  approxi- 
mately 5  per  cent  of  the  whole  number  obtained,  and  may  be  accepted 
as  representing  the  best  results  obtainable  under  any  combination  of 
stack  and  nozzle  involved  by  the  experiments. 

TABLE  LVI. 

STACK  AND  NOZZLE  COMBINATION  GIVING  BEST  RESULTS. 


Speed, 
Miles  per 
Hour. 

Cut-off 
Notch. 

Draft, 
Inches  of 
Water. 

Nozzle 
Num- 
ber. 

Stack 
Num- 
ber. 

Speed, 
Miles  per 
Hour. 

Cut-off 
Notch. 

Draft, 
Inches  of 
Water. 

Nozzle 
Num- 
ber. 

Stack 
Num- 
ber. 

20 

5 

3.4 

2 

7-D 

50 

5 

5.5 

1 

8-D 

20 

5 

3.3 

1 

6-D 

50 

5 

5.4 

1 

6-D 

20 

5 

3.3 

2 

4-D 

50 

5 

5.4 

2 

6-D 

20 

5 

3.2 

3 

7-D 

50 

5 

5.4 

3 

8-D 

20 

5 

3. 

5 

4-D 

50 

5 

5.3 

1 

4-D 

20 

5 

3. 

2 

6-D 

60 

5 

6.6 

2 

4-D 

20 

5 

3. 

3 

6-D 

60 

5 

6.4 

1 

8-D 

20 

5 

3. 

4 

6-D 

60 

5 

6.2 

1 

6-D 

20 

5 

3. 

2 

8-D 

60 

5 

6.1 

1 

4-D 

30 

5 

4.3 

2 

4-D 

60 

5 

6.0 

2 

8-D 

30 

5 

4.3 

1 

6-D 

40 

3 

3.6 

2 

8-D 

30 

5 

4.1 

2 

7-D 

40 

3 

3.2 

1 

8-D 

30 

5 

4.0 

2 

6-D 

40 

3 

3.1 

1 

4-D 

30 

5 

4.0 

3 

7-D 

40 

3 

3.0 

3 

6-D 

30 

5 

4.0 

3 

7-D 

40 

3 

3.0 

3 

8-D 

30 

5 

4.0 

1 

8-D 

40 

3 

3.0 

6-C 

30 

5 

4.0 

2 

8-D 

40 

5 

5.3 

4-D 

30 

5 

4.0 

3 

8-D 

40 

5 

5.0 

8-D 

40 

5 

5.2 

3 

6-D 

40 

5 

4.8 

8-D 

40 

5 

5.0 

2 

4-D 

40 

5 

4.7 

6-D 

40 

5 

5.0 

2 

6-D 

40 

5 

4.6 

8-C 

40 

5 

4.9 

1 

8-D 

40 

7 

7.8 

8-D 

40 

5 

4.8 

1 

6-D 

40 

7 

7.6 

4-D 

40 

5 

4.7 

2 

7-D 

40 

7 

7.6 

6-D 

40 

5 

4.7 

2 

8-D 

40 

7 

7.6 

2 

8-D 

40 

5 

4.6 

2 

4-C 

40 

7 

7.4 

2 

6-D 

This  table  shows  at  a  glance  that  all  the  highest  draft  readings  were 
obtained  with  the  D  stacks,  which  designation  embraces  those  of 


THE  FRONT  END.  241 

greatest  length  employed  in  the  experiments  (56 J  inches).  The  C 
stacks,  which  are  10  inches  shorter  than  the  D  stacks,  appear  in  the 
table  but  three  times,  and  in  two  of  these  instances  the  draft  is  inferior 
to  that  given  by  the  higher  stack.  Stacks  bearing  even  numbers  are 
tapered,  and  those  bearing  odd  numbers  are  straight.  It  is  noteworthy 
that  practically  all  of  the  numbers  appearing  in  the  table  of  best  results 
represent  tapered  stacks.  The  stack  numbers  which  most  frequently 
appear  are  4,  6,  and  8,  representing  a  diameter  at  the  choke  of  11J, 
13f ,  and  15f  inches  respectively. 

Resorting  now  to  a  detailed  study  covering  all  the  various  heights 
and  diameters  of  stacks  experimented  upon,  and  dealing  first  with  the 
straight  stacks,  the  large  spots  upon  Figs.  133  to  136,  inclusive,  show 
the  best  diameters  for  each  height  of  stack  experimented  upon,  and  for 
each  height  of  nozzle  employed.  Thus,  disregarding  for  the  present 
the  oblique  line  drawn  upon  these  diagrams,  the  large  spots  upon  Fig. 
133  show  the  best  diameter  of  stack  for  each  height  of  nozzle  em- 
ployed, when  the  height  of  the  stack  is  limited  to  26J  inches;  those 
upon  Fig.  134  show  the  best  diameter  of  stack  for  each  height  of  nozzle 
employed,  when  the  height  of  stack  is  limited  to  36J  inches.  In  each 
case  the  large  spots  represent  the  diameter  of  the  experimental  stacks 
giving  the  highest  draft.  The  points  are  not  located  from  curves. 
Since  the  experimental  stacks  varied  one  from  another  by  steps  of  2 
inches,  the  exact  diameter  represented  by  a  given  large  spot  does  not 
necessarily  represent  the  most  desirable  diameter  for  the  conditions 
defined;  that  we  will  hereafter  proceed  to  find. 

Continuing  to  give  attention  to  the  black  spots  of  the  diagrams,  it 
will  be  noticed  that  some  of  the  larger  spots  have  smaller  spots  con- 
nected with  them  by  a  horizontal  line.  In  some  cases  there  is  a  small 
spot  on  one  side  of  the  larger  spot,  and  in  other  cases  there  are  smaller 
spots  on  both  sides.  These  smaller  spots  indicate  that  the  next  sized 
stack  on  one  or  the  other  sides,  or  on  both  sides  of  the  best  experimental 
stack  gave  results  almost  as  good  as  the  best.  Instead  of  having  a 
series  of  points  representing  the  experimental  data,  we  have  a  series 
of  lines  which  may  be  employed  to  establish  a  zone  of  good  per- 
formance. Concerning  the  width  of  this  zone,  it  should  be  noted  that 
the  lines  span  but  half  the  distance  between  the  position  of  the  stack 
which  was  best  and  that  which  is  almost  as  good;  also,  that  in  cases 
where  stacks  on  one  or  the  other  side  of  the  best  were  not  almost  as 
good,  no  line  whatever  has  been  drawn. 

A  review  of  the  diagrams,  Figs.  133  to  136,  shows  at  a  glance  that 


242 


LOCOMOTIVE  PERFORMANCE. 


the  largest  straight  stack  (15f  inches),  while,  perhaps,  sufficient  in  di- 
ameter for  the  least  height  (Fig.  133),  was  quite  insufficient  for  the 
lower  nozzle  position  when  the  stack  height  was  increased  beyond  26| 
inches.  This  is  best  shown  by  Fig.  136.  The  best  results  in  connec- 
tion with  this  stack  were  obtained  for  the  four  lowest  positions  of  the 


Stack  A 


Height  26'^ 


Stack  B 


Height  36^ 


\ 

^ 

^ 

^ 

\ 

S 

\ 

1 

0 

1 

2 

1 

1 

1 

I 

Xl 

s 

\ 

\ 

\ 

\ 

3 

'  -  ^ 

\ 

2- 

'-\ 

\ 

\ 

\ 

i 

0 

1 

2 

1 

1 

1 

I 

.  ^ 

1 

! 

Stack  Diameter.  Inches 

FIG.  133. 


Stack  Diameter.  Inches 

FIG.  134. 


•exhaust-pipe.  When  the  tip  of  the  exhaust-pipe  was  5  inches  above 
the  center  line  of  the  boiler,  the  next  smaller  stack  was  almost  as  good, 
but  for  the  lower  nozzles  (3,  2,  and  1),  the  largest  stack  was  in  a  marked 
degree  better  than  any  which  were  smaller,  justifying  the  conclusion 
that  if  a  stack  as  large  as  18  inches  in  diameter  had  been  tried,  the 


Stack  C 


Height  46 


Stack  D 


\  9 

\ 

\  * 

^ 

x 

\ 

"\ 

So 

\ 

\ 

1 

0 

1 

2 

i 

4 

*! 

16 

1 

\ 

s 

-     Height  .56^* 


\ 

^ 

\ 

s, 

\J 

\ 

\ 

1 

0 

1 

2 

1 

I 

1 

1 

1 

s 

Stack-Diameter.  Inches 


FIG.  135. 


Stack  Diameter.  Inches 

FIG.  136. 


results  obtained  therefrom  would  have  been  given  a  place  on  the 
diagram. 

Best  results  obtained  from  tapered  stacks,  plotted  in  a  manner 
already  described  in  considering  the  action  of  the  straight  stack, 
are  presented  as  Figs.  137  to  140  inclusive.  In  this  case,  however,  the 
several  diameters  of  stack  experimented  upon  cover  a  range  sufficiently 


THE  FRONT  END. 


243 


wide  to  permit  the  selection  of  the  best  stack  for  all  heights  of  stacks 
in  combination  with  all  heights  of  nozzles. 

1 1 6.  Relation  of  Height  to  Diameter  of  Stack. — The  problem  of 
stack  design,  as  disclosed  by  the  data  already  presented,  is  not  to  be 
regarded  as  one  requiring  a  high  degree  of  refinement.  The  data  show 


Stack  A                                       Height  26  >£ 

7~ 

5— 

\ 

\I 

\ 

\ 

\i 

\ 

\ 

i 

| 

1 

1 

t 

\' 

1 

1 

1 

8 

Stack  B 


Height  36?i 


Stack  Diameter.  Inches 

FIG.  137. 


\ 

\ 

\J 

4 

\ 

\ 

V, 

\ 

s 

\ 

i 

0 

1 

2 

1 

1 

0 

1 

S 

Stack  Diameter.   Inches 

FIG.  138. 


that  two  stacks  varying  as  much  as  2  inches  in  diameter  sometimes 
give  results  which  are  almost  identical.  It  happens  in  some  cases,  also, 
that  a  stack  of  a  diameter  which  gives  maximum  results  is  almost 
equaled  in  its  performance  by  a  stack  2  inches  less,  and  also  by  a  stack 
2  inches  greater  in  diameter.  In  such  a  case  a  variation  of  4  inches 


Stack  C 


Height  46  !£ 


Stack  D 


Height  ')f>}4 


-  i 

\ 

5 

\ 

1 

\ 

3 

\ 

2 

> 

\ 

l 

} 

1 

l 

1 

1 

5 

1 

S 

-.N 

\ 

2 

| 

\ 

\ 

\» 

'\ 

\ 

1 

0 

1 

i 

r'4 

\   i 

16 

1 

S 

Stack  Diameter    Inches 

FIG.  139. 


Stack  Diameter.  Inches 
FIG.  140. 


in  the  diameter  of  the  stack  appears  not  to  be  significant.  This  is  only 
true,  however,  with  certain  heights  of  stacks  in  combination  with  cer- 
tain heights  of  nozzles,  and,  as  will  be  hereafter  shown,  the  occurrence 
of  such  cases  is  more  frequent  in  the  case  of  tapered  stacks  than  in  the 
case  of  straight  stacks. 

It  is  evident,  therefore,  that  it  will  be  impracticable  to  determine 
within  a  small  fraction  of  an  inch  the  diameter  of  stack  corresponding 


244  LOCOMOTIVE  PERFORMANCE. 

with  any  given  height  of  stack  and  position  of  nozzle,  which  can  be 
said  to  accurately  represent  the  experimental  results,  for  it  is  some- 
times hard  to  say  whether  one  or  another  of  two  stacks  is  the  better. 
For  the  purpose,  therefore,  of  reducing  the  various  discordant  elements 
to  order,  that  a  general  law  may  be  formulated,  no  harm  will  be  done 
by  employing  a  fair  degree  of  liberality  in  interpreting  the  data. 

Straight  Stacks. — In  order  that  the  best  relation  of  diameter  and 
height  of  stack  may  be  stated,  it  will  at  first  be  necessary  to  eliminate 
variations  in  the  height  of  the  nozzles.  Comparisons  will,  therefore, 
first  be  based  upon  results  obtained  with  nozzle  No.  3,  this  being  the 
nozzle  for  which  the  tip  is  on  the  center  line  of  the  boiler.  From  a 
study  of  the  plotted  spots  of  Fig.  133,  it  has  been  assumed  that,  when 
the  exhaust-tip  is  on  the  center  of  the  boiler,  and  the  height  of  the  stack 
is  26J  inches,  the  most  satisfactory  diameter,  as  disclosed  by  the  data, 
is  15  inches,  and  a  circle  has  been  struck  on  the  diagram  (Fig.  133)  to 
represent  this  value.  Similarly,  from  Fig.  134,  it  appears  that  when 
the  exhaust-tip  is  on  the  center  of  the  boiler  and  the  height  of  the  stack 
is  36^  inches,  the  most  satisfactory  diameter  is  15.66,  and  a  circle,  the 
location  of  which  corresponds  with  this  value,  has  been  struck  on  this 
diagram.  In  the  same  manner  for  the  46J-inch  stack,  the  circle  has 
been  struck  to  represent  a  diameter  of  16.33  inches,  and  for  the  56J- 
inch  stack  the  circle  has  been  struck  to  represent  a  diameter  of  17 
inches.  These,  then,  are  assumed  to  be  the  best  diameters  of  stacks 
for  each  of  the  several  heights  experimented  upon,  when  the  exhaust- 
nozzle  is  on  the  center  line  of  the  boiler. 

Stating  these  facts  in  the  form  of  equations,  in  which  d  is  the  diam- 
eter of  stack  in  inches,  we  have,  for  the  engine  experimented  upon,  the 
following : 

For  straight  stacks  26£  inches  high: 

d1  =  15  =  .28X54. 

For  straight  stacks  36|  inches  high : 

d2  =  15.66  =  .29X54. 
For  straight  stacks  46J  inches  high : 

d3  =  16.33  =  .30X54. 
For  straight  stacks  56£  inches  high : 

d4  =  17  =  .31X54. 


THE  FRONT  END.  24$ 

For  all  of  these  values  the  exhaust-tip  was  on  the  center  of  the  boiler, 
and  the  diameter  of  the  front  end  of  the  boiler  experimented  upon  was 
54  inches.  If,  now,  we  may  assume  that  the  data  obtained  from  the 
engine  experimented  upon  is  applicable  to  engines  having  boilers  of 
different  diameters,  and  if  we  may  assume  also  that  in  applying  the 
data  to  other  engines,  we  may  use  the  diameter  of  the  boiler  as  a, 
unit  of  measure,  then  the  diameter  of  stack  for  any  boiler  whatsoever 
which  has  the  exhaust-tip  on  the  center  line  should  be  represented 
by  equations  in  which  D,  the  diameter  of  the  inside  of  the  front  end, 
is  substituted  for  the  value  54  in  the  preceding  equations.  The  result 
is  as  follows: 

For  straight  stacks  26^  inches  high  : 


For  straight  stacks  36J  inches  high  : 

d?2  =  15.66  =  .  29  XD. 

For  straight  stacks  46  J  inches  high  : 

d3  =  16.33  =  .  30  XD. 

For  straight  stacks  56^  inches  high: 


If,  now,  an  expression  can  be  found  which  maybe  substituted  for  the 
coefficient  of  D,  and  which  will  represent  the  height  of  stack  in  inches 
in  each  of  the  four  equations,  it  will  be  possible  to  write  a  single  equa- 
tion in  the  place  of  four.  That  this  may  be  more  readily  accomplished, 
the  values  representing  best  diameters  with  which  we  have  been  deal- 
ing were  so  chosen  that,  while  doing  no  violence  to  the  experimental 
data,  they  will,  when  plotted  in  terms  of  height  of  stack,  fall  upon 
the  same  straight  line,  all  as  shown  by  Fig.  141.  This  fact  makes 
it  possible  to  write  in  simple  form  a  general  equation  expressing 
the  relation  thus  defined.  Thus,  by  Fig.  141,  it  is  apparent  that 
when  the  stack  height  is  zero,  the  diameter  is  equal  to  something 
over  13  inches  (more  exactly,  13.23),  and  the  slope  of  the  line  connect- 
ing the  several  experimental  points  is  such  that  with  each  inch  height 
of  stack,  the  diameter  increases  .00123  inch  X  54.  We  may  there- 
fore write  as  the  coefficient  of  D,  in  the  four  preceding  equations, 

(.246  +  .00123#), 
in  which  H  is  the  height  of  the  stack  in  inches. 


246 


LOCOMOTIVE  PERFORMANCE. 


We  may,  therefore,  write  for  any  straight  stack  when  the  exhaust- 
nozzle  is  on  the  center  line  of  the  boiler. 


d  being  the  diameter  of  the  stack  in  inches  when  the  exhaust-nozzle  is 
on  the  center  line  of  boiler,  H  the  height  of  the  stack  in  inches,  and  D 
the  diameter  of  the  front  end  of  the  boiler  in  inches.  Modification  in 
the  form  of  this  equation  to  satisfy  the  condition  arising  from  varying 
heights  of  exhaust-nozzle  will  be  hereafter  considered. 


Diameter  of  Stack,   Inches 

FIG.  141. 

Tapered  Stacks. — The  best  results  attending  the  use  of  the  tapered 
stacks  of  each  different  height  experimented  upon,  in  connection  with 
the  seven  different  heights  of  exhaust-nozzles,  appear  in  Figs.  137  to 
140  inclusive.  In  these  diagrams  the  experimental  results  are  shown 
by  means  of  black  spots  connected  by  horizontal  lines  in  the  manner 
already  described  in  connection  with  the  straight  stack.  When  two 
stacks  give  equally  good  results,  both  points  are  located  and  the  spots 
connected  by  a  horizontal  line;  and  where  a  larger  or  smaller  stack 
gives  results  almost  as  good  as  the  best,  a  line  is  extended  in  its  direc- 
tion, terminating  in  a  small  spot  midway  between  that  representing 


THE  FRONT  END.  247 

the  best  stack  and  the  position  representing  the  stack  which  is  almost 
as  good. 

Proceeding,  as  in  the  case  of  the  straight  stacks,  to  locate  a  repre- 
sentative point  in  line  with  nozzle  No.  3,  which  will  fairly  represent  the 
experimental  data,  choice  has  been  made  of  the  diameter  13J  inches, 
and  a  circle  drawn  upon  all  diagrams  while  at  this  diameter.  It  ap- 
pears, therefore,  that  an  important  conclusion  to  be  derived  from  the 
experimental  data  is  to  the  effect  that  a  tapered  stack  having  a  least 
diameter  of  13^  inches  gives  maximum  results  for  all  heights  of  stack 
between  the  limits,  of  26J  and  56^  inches.  In  other  words,  unlike  the 
straight  stack,  the  diameter  of  the  tapered  stacks  does  not  need  to  be 
varied  with  changes  in  the  height. 

Stating  this  fact  in  the  form  of  an  equation,  therefore,  we  have  for 
a  tapered  stack  upon  the  Purdue  engine,  the  diameter  of  the  boiler 
of  which  is  54  inches,  the  following  : 

da  =  13.5; 
also  da  =  .25  X  54  inches. 

Assuming  that  the  results  thus  obtained  from  the  experimental 
engine  may  be  applied  to  other  engines  having  different  diameters  of 
boilers,  and  using  the  diameter  of  the  boiler  as  a  unit  of  measure,  we 
may  write  for  all  locomotives,  and  for  all  heights  of  stack  where  the 
exhaust-tip  is  on  the  center  line  of  the  boiler: 


in  which  d  is  the  least  diameter  of  the  tapered  stack  when  the  ex- 
haust-tip is  on  the  center  line  of  the  boiler,  and  D  is  the  diameter 
of  the  front  end  of  the  boiler. 

117.  The  Effect  of  Changes  in  the  Height  of  the  Exhaust-nozzle 
upon  the  Diameter  of  the  Stack.  —  For  the  purpose  of  passing  from 
the  results  obtained  from  the  experimental  engine  to  those  to  be  ex- 
pected from  engines  having  boilers  of  other  diameters,  using  the  boiler 
diameter  as  a  unit  of  measure,  it  has  been  necessary  thus  far  to  deal 
with  conditions  for  which  the  parts  are  symmetrically  arranged.  It 
is  for  this  reason  that  the  central  position  of  the  nozzle  is  the  only  posi- 
tion which  has  been  employed.  We  may  now  consider  the  influence 
upon  the  diameter  of  the  stack  resulting  from  changes  in  the  height  of 
the  nozzle. 

The  points  represented  by  the  circles  (Figs.  133  to  140),  and  which 


248  LOCOMOTIVE  PERFORMANCE. 

have  been  the  basis  of  equations  thus  far  written,  have  been  so  located 
that  it  is  possible  to  draw  through  each  of  them  a  straight  line,  which 
will  fairly  represent  the  best  diameter  of  stack  for  all  heights  of  nozzles. 
The  oblique  line  which  appears  in  the  several  figures  may  be  regarded 
,as  such  a  line.  It  now  remains  to  find  an  expression  for  this  line  which 
can  be  added,  as  a  new  term,  to  the  equation  which  has  already  been 
deduced,  for  the  purpose  of  modifying  the  final  results  as  demanded  by 
the  differences  in  results  obtained  when  changes  are  made  in  the  height 
of  the  nozzle. 

Straight  Stacks.  —  In  Figs.  133  to  136  inclusive,  representing  the 
straight  stacks,  the  oblique  lines  representing  the  relationship  between 
diameter  of  stack  and  height  of  nozzle,  as  disclosed  by  the  experimental 
data,  have  all  been  drawn  at  a  constant  angle.  The  slope  of  the 
line  is  such  that,  assuming  the  effect  of  the  nozzle  in  position  3  to  be 
zero,  the  effect  upon  the  diameter  of  the  stack  of  each  inch  change 
in  the  height  of  the  exhaust-nozzle  equals  .19  of  an  inch.  It  is  evident 
that  this  correction  will  effect  an  increase  in  the  diameter  of  the  stack 
when  the  nozzle  position  is  below  the  center  line  of  the  boiler,  and  a 
decrease  in  the  diameter  of  the  stack  when  the  exhaust-nozzle  is  above 
the  center  line  of  the  boiler.  We  may,  therefore,  write  as  a  new  term 
in  the  equation,  giving  the  best  diameter  of  a  straight  stack, 


in  which  h  is  the  distance  in  inches  between  the  center  line  of  the  boiler 
.and  the  exhaust-  tip,  the  sign  preceding  this  term  being  positive  when 
h  is  the  distance  below  the  center  line,  and  negative  when  h  is  the  dis- 
tance above  the  center  line. 

Tapered  Stacks.  —  By  a  similar  process  it  may  be  shown  that  the 
effect  of  changes  in  the  height  of  nozzle  on  the  diameter  of  a  tapered 

;Stack  is  expressed  by 

.16ft, 

the  sign  preceding  the  term  being  positive  when  h  is  the  distance 
below  the  center  line,  and  negative  when  h  is  the  distance  above  the 
center  line. 

118.  Equations  giving  Stack  Diameters  for  any  Height  of 
Stack  between  the  Limits  of  26  and  56  Inches,  and  any  Height 
of  Nozzle  between  the  Limits  of  10  Inches  below  the  Center  of  the 
Boiler,  and  20  Inches  above  the  Center  of  the  Boiler,  and  for  any 
Diameter  of  Front  End.  —  Combining  the  expressions  of  the  two  pre- 
ceding paragraphs,  we  may  have  equations  giving  diameter  of  stack 


THE  FRONT  END.  249 

in  terms  of  its  height,  diameter  of  front  end,  and  the  distance  between 
the  center  line  of  the  boiler  and  the  top  of  the  exhaust-tip.  These 
several  equations  obviously  are  the  equations  of  the  oblique  lines  ap- 
pearing in  the  corresponding  diagrams,  Figs.  133  to  140.  They  are  as 
follows  : 

For  straight  stacks: 

When  the  exhaust-nozzle  is  below  the  center  line  of  the  boiler 

d  =  (.246  +  .00123H)D  +  .19ft. 
When  the  exhaust-nozzle  is  above  the  center  line  of  the  boiler 

d  =  (.246  +  .00123#)£>  -  .19ft. 

When  the  exhaust-nozzle  is  on  the  center  line,  ft  is  equal  to  zero  and 
the  equation  becomes 


For  tapered  stacks: 

When  the  nozzle  is  below  the  center  line  of  the  boiler 


When  the  nozzle  is  above  the  center  line  of  the  boiler 
d  =  .25Z)-.16ft. 

When  the  nozzle  is  on  the  center  line  of  the  boiler,  ft  becomes  zero, 
and 

d  =  .25D. 

In  all  of  these  equations  d  is  the  diameter  of  the  stack  in  inches.  For 
the  tapered  stack  it  is  the  least  diameter  or  diameter  of  choke.  H  is 
the  height  of  stack  in  inches,  and  for  maximum  efficiency  should  always 
be  given  as  large  a  value  as  conditions  will  admit.  D  is  the  diameter 
of  the  front  end  of  the  boiler  in  inches,  and  ft  the  distance  between 
center  line  of  boiler  and  the  top  of  the  exhaust-  tip. 

If  D  in  the  several  equations  is  made  equal  to  54,  the  diameter  of 
the  front  end  of  the  Purdue  locomotive,  the  equations  will  give  results 
identical  with  those  which  are  assumed  to  represent  the  maximums 
obtained  in  the  course  of  the  experiments.  How  far  they  should  be 
employed  in  the  manner  which  has  been  indicated  for  an  engine  having 
a  boiler  different  in  size  cannot,  of  course,  be  stated  with  certainty, 


250 


LOCOMOTIVE  PERFORMANCE. 


though  it  seems  clear  that,  where  the  conditions  surrounding  stack 
and  nozzle  are  similar,  they  may  be  depended  upon  to  give  satisfactory 
results  for  any  diameter  of  front  end  now  in  use,  or  likely  soon  to  come 
into  use.  Notwithstanding  the  short  time  which  has  elapsed  since 
the  first  publication  of  the  equations  which  have  been  given,  they 
have  already  been  extensively  employed  in  service,  with  satisfactory 
results.  The  conditions  which  should  be  observed  in  their  use  is  best 
shown  by  Figs.  142  and  143. 


FIG.  142. 

In  this  connection,  also,  it  should  be  noted  that  it  is  not  claimed 
that  the  plain  stack  and  nozzle,  as  shown,  will  give  better  results  than 
some  other  arrangement,  but  merely  that  when  the  plain  stack  and 
nozzle  are  used  the  equations  will  give  the  best  relation  of  diameter  to 
height  which  is  obtainable.  It  is  this  question  only  that  the  experi- 
ments were  designed  to  cover.  Whether,  for  example,  as  a  general 
proposition,  the  application  of  draft-  or  petticoat-pipes  will  improve  the 
draft,  or  whether  they  will  affect  the  relation  of  height  and  diameter 
of  stack  as  already  established,  cannot  be  determined  from  the  present 
work. 


THE  FRONT  END. 


251 


119.  Unavoidable  Loss  in  Draft  with  Deduction  in  Height  of 
Stack. — The  equations  already  presented,  together  with  the  tabulated 
statements  based  thereon,  are  assumed  to  give  the  best  diameter  for  a 
stack  of  any  given  height.  They  cannot  be  depended  upon  to  give 
results  which  will  always  be  satisfactory  under  conditions  which  greatly 
limit  or  restrict  the  height.  In  general,  the  best  draft  obtainable  from 
a  short  stack  is  inferior  to  that  obtained  from  a  longer  stack.  The 
most  that  can  be  done  when  the  limit  of  height  has  been  fixed  is  to 


FIG.  143. 

determine  a  diameter  which,  in  combination  with  that  height,  will  give 
best  results.  It  is  this,  and  this  only,  that  the  equations,  and  the 
tables  based  thereon,  are  assumed  to  do. 

The  rate  at  which  the  draft  diminishes  with  each  reduction  in  height 
of  stack  is  indicated  by  Figs.  144  to  147,  presenting  results  plotted  in 
terms  of  draft  and  stack  height.  In  explanation  of  these  figures,  it 
should  be  noted  that  the  stack  heights  represented  are:  Base,  16 J 
inches;  A,  26  J  inches;  B,  36J  inches;  C,  46J  inches;  and  D  56J 
inches.  Fig.  144  gives  results  with  the  smallest  tapered  stack  in  com- 
bination with  the  lowest  nozzle;  Fig.  145,  those  for  the  largest  tapered 
stack  in  combination  with  the  lowest  nozzle;  and  Figs.  146  and  147 
those  for  the  smallest  and  largest  tapered  stacks  respectively,  for  a 


252 


LOCOMOTIVE  PERFORMANCE. 


series  of  tests  at  different  cut-offs.     In  all  of  these  figures  it  will  be  seen 
that  there  is  a  marked  decrease  in  the  draft  obtained  for  each  reduction 


Nozzle-l  S"tack-2 


Nozzle-1  Stack-8 


Stack  Heights 

FIG.  144. — Small  Tapered  Stack. 


Stackjtieigh.ts 

FIG.  145.— Large  Tapered  Stack. 


in  the  height  of  stack.    This  is  the  more  significant  when  it  is  consid- 
ered that  these  diagrams  represent  only  tapered  stacks,  and  that  the 


Nozzle-    Stack-2 


y 

O 
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i 

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£ 

& 

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J 

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—16 

I* 

K- 

ise 

-26 

f 

*- 

-36 

t 

-4<- 

e 

-56 

[ 

*- 

— 

Stack  Heights 

FIG.  146.— Small  Tapered  Stack. 


Nozzle-1  Stack-8  ^X^ 

|  c&*5 

)/ 

t 

Vx 

^ 

X^ 

*>• 

^ 

4r, 

^f 

£ 

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—  1( 

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se 

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i 

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-565^- 
D 

Stack  Heights 

}.  147.— Large  Tapered  Stack, 


diameter  of  the  choke  of  such  stacks  is  not  required  to  be  changed 
when  the  stack  is  varied  in  height.  It  is  clear,  therefore,  that  these 
diagrams  confirm  the  statement  already  made  to  the  effect  that  a 


THE  FRONT  END. 


253 


short  stack,  however  well  designed,  must  be  inferior  in  Its  draft-pro- 
ducing qualities  to  a  longer  stack  of  good  design.  There  is,  in  fact, 
nothing  in  the  relation  of  diameter  to  height,  or,  so  far  as  the  investi- 
gation has  proceeded,  in  the  form  of  the  stack  itself,  which  can  be 
accepted  as  a  complete  substitute  for  height.  Again,  it  can  be  shown 
that  this  loss  in  draft  with  changes  in  height  of  stack  does  not  depend 
upon  the  height  of  the  nozzle.  Thus,  Table  LVII.  represents  a  sum- 
mary of  results  in  connection  with  all  heights  of  the  smallest  tapered 
stack  in  combination  with  all  heights  of  nozzle.  The  table  shows  that, 
whatever  the  height  of  the  nozzle,  the  loss  in  draft  under  the  conditions 
represented  in  passing  from  the  D,  or  56J-inch  height,  to  the  A,  or  26J- 
inch  height,  is  a  fixed  quantity,  and  under  the  conditions  of  the  tests 
referred  to  is  approximately  represented  by  1.6  inches  of  water.  Thus, 
for  the  nozzle  No.  1,  it  is  1.7  inches;  for  the  nozzle  No.  3,  1.4  inches; 
for  the  nozzle  No.  5,  1.8  inches;  for  the  nozzle  No.  7,  1.6  inches. 

TABLE  LVII. 

BEST  DRAFT  OBTAINABLE  UNDER  CONDITIONS  OF  CONSTANT  SPEED 
AND  CUT-OFF  WITH  DIFFERENT  HEIGHTS  OF  STACK  IN  CONNEC- 
TION WITH  DIFFERENT  HEIGHTS  OF  EXHAUST-NOZZLE. 


Nozzle. 

1 

2 

3 

4 

5 

6 

7 

6 

g 

o5 

8 

g 

g 

g 

fl 

CH 

fH 

c 

Q 

g 

£j 

_^ 

£ 

.. 

£ 

. 

g 

J 

e 

. 

£ 

^j 

£ 

£ 

8 

| 

| 

i 

1 

1 

i 

£ 

i 

9) 

| 

V 

i 

«§ 

Q 

5 

Q 

Q 

G 

Q 

Q 

Q 

Q 

Q 

Q 

Q 

Q 

Q 

Stack  2-D.  .  . 

4.0 

4.2 

4.0 

3.9 

4.0 

3.4 

3.2 

Stack  2-C.  .  . 

3.5 

.5 

3.8 

.4 

3.7 

.3 

3.5 

.4 

3.5 

.5 

3.1 

.3 

2.7 

.5 

Stack  2-B.  .  . 

3.1 

.4 

3.2 

.6 

3.3 

.4 

3.0 

.5 

2.9 

.6 

2.5 

.6 

2.2 

.5 

Stack  2-A.  .  . 

2.3 

.8 

2.4 

.8 

2.6 

.7 

2.4 

.6 

2.2 

.7 

2.0 

.5 

1.6 

.6 

Total    differ- 

ence   

1.7 

1.8 

1.4 

1.5 

1.8 

1.4 

1.6 

It  is  difficult  to  find  a  quantitative  measure  for  the  loss  of  draft 
resulting  from  reduction  in  height  of  stack  which  will  be  of  general 
application.  The  extent  of  such  loss  is,  however,  suggested  by  the 
slope  of  the  lines  in  the  figures  already  referred  to,  and  by  the  differ- 
ences in  Table  LVII.  The  general  conclusion  is,  however,  clear.  It 
is  apparent  that  the  shorter  stacks  are  far  inferior  to  those  of  greater 
length,  and  that  the  maintenance  of  draft  values  in  connection  there- 
with must  necessarily  involve  the  application  of  additional  mechanism, 
•or  an  increase  in  the  energy  of  the  exhaust-jet.  The  study  here  de- 


254  LOCOMOTIVE  PERFORMANCE 

scribed  does  not  suffice  to  indicate  what  should  be  the  character  of  such 
additional  mechanism  nor  the  extent  of  the  necessary  increase  in  the 
energy  of  the  exhaust-jet.  It  is,  however,  altogether  possible  that  the 
adoption  of  some  form  of  inside  stack  or  of  draft-pipes  may  make  good 
the  loss  resulting  from  the  diminished  length  of  outside  stack. 

1 20.  Relative  Advantage  of  Straight  and  Tapered  Stacks. — 
But  two  forms  of  stacks  were  employed  in  the  experiments  under  dis- 
cussion, one  being  perfectly  cylindrical,  and  hence  referred  to  as  the 
straight  stack;  the  other  having  the  form  best  shown  by  Fig.  122,  and 
generally  referred  to  as  the  tapered  stack.  This  tapered  stack  has  its 
least  diameter,  or  choke,  at  a  point  16^  inches  from  the  bottom,  and 
increases  in  diameter  uniformly  above  this  point,  the  angle  of  the  sides 
being  the  same  for  all  stacks,  and  the  divergence  being  at  the  rate  of 
2  inches  in  diameter  for  each  foot  in  length.  This  divergence  corres- 
ponds with  that  which  was  found  best,  as  a  result  of  the  von  Borries- 
Troske  tests.  The  most  noteworthy  difference  in  results  obtained 
from  the  two  contours  is  to  be  found  in  the  increased  capacity  of  the 
tapered  stack.  Thus,  No.  2  stack  (9f  inches  diameter),  which  is  the 
smallest  of  the  tapered  stacks,  gives  draft  values  which  are  two  or  three 
times  as  great  as  those  obtained  with  No.  1,  which  is  a  straight  stack 
of  the  same  diameter.  While  the  results  from  No.  2  are  none  of  them 
sufficiently  meritorious  to  warrant  a  place  in  the  table  of  best  results 
(Table  LVII.),  they  give  a  close  approach  thereunto.  The  two  smaller 
diameters  of  straight  stacks  Nos.  1  and  3  (9f  and  11}  inches  diame- 
ter) are  both  far  too  small  to  yield  results  which  are  to  be  regarded 
as  satisfactory,  the  capacity  of  these  stacks  being  insufficient  for  the 
work  expected  of  them.  Speaking  in  rather  general  terms,  it  may  be 
said  that  a  tapered  stack  having  a  diameter  of  choke  of  9f  inches  has 
as  great  a  capacity  as  a  cylindrical  stack  of  13}  inches.  Again,  only 
the  largest  diameter  of  straight  stack  No.  7  (15}  inches  diameter)  has 
a  place  in  the  table  of  best  results,  whereas  all  diameters  of  the  tapered 
stack,  excepting  the  least,  find  places  in  the  table.  It  is  of  interest  to 
note  that  with  the  low  nozzle,  tapered  stack  6  B  (least  diameter,  13f 
inches;  total  height,  36J  inches)  gives  identical  results  with  straight 
stack  1C  (diameter,  15}  inches;  height,  46J  inches),  the  tapered  stack 
being  10  nches  lower  and  2  inches  less  in  diameter  than  the  straight 
stack. 

It  has  been  stated  that  whereas  for  best  results  the  diameter  of  the 
straight  stack  must  change  for  every  change  in  height,  that  of  the  tap- 
ered stack  remains  constant  for  all  heights.  In  this  connection  it  is 


THE  FRONT  END.  255 

important  to  remember  that  the  diameter  of  the  tapered  stacks  referred 
to  is  the  diameter  of  the  choke  (least  diameter).  As  a  matter  of  fact, 
if  designs  based  on  the  equations  which  have  been  deduced  were  to  be 
superimposed,  they  would  show  that  while  the  tapered  stack,  as  com- 
pared with  the  straight  stack,  is  of  lesser  diameter  at  the  choke,  the 
diameter  of  its  top  would  generally  exceed  that  of  the  straight  stack. 

In  general,  it  would  seem  that  the  tapered  stack  is  less  susceptible 
to  minor  changes  of  proportion,  both  of  the  stack  itself  and  of  the  sur- 
rounding mechanism,  than  the  straight  stack.  Thus,  a  variation  of 
an  inch  or  two  in  the  diameter  of  the  tapered  stack  affects  the  draft 
less  than  a  similar  change  in  the  diameter  of  the  straight  stack.  Again, 
the  tapered  stack  is  generally  less  affected  by  variations  in  the  height 
of  the  nozzle,  so  that  altogether  it  appears  quite  contrary  to  the  ex- 
pectation of  the  experimenter,  that  the  use  of  the  tapered  stack  gives 
a  greater  degree  of  flexibility  in  the  design  of  the  dependent  parts. 
For  these  reasons  the  tapered  form  is  altogether  preferable  to  the 
straight  form. 

121.  A  Summary  of  Results. — The  most  important  conclusions 
to  be  drawn  from  the  experiments  described  may  be  stated  as  follows: 

1.  The  jet  acts  upon  the  smoke-box  gases  in  two  ways;  first,  by 
frictional  contact,  it  induces  motion  in  them;  and,  second,  it  enfolds 
and  entrains  them. 

2.  The  action  of  the  jet  upon  the  smoke-box  gases  is  to  draw  them 
to  itself,  so  that  the  flow  within  the  front  end  is  everywhere  toward 
the  jet. 

3.  The  action  of  the  jet  is  not  dependent  upon  the  impulses  result- 
ing from  individual  exhausts.     Draft  can  be  as  well  produced  by  a 
steady  flow  of  steam  as  by  the  intermittent  action  of  the  exhaust. 

4.  Draft  resulting  from  the  action  of  the  jet  is  nearly  proportional 
to  the  weight  of  steam  exhausted  per  unit  of  time.     It  does  not  depend 
upon  the  speed  of  the  engine  nor  the  cut-off  of  steam  from  the  cylin- 
ders, except  in  so  far  as  these  affect  the  weight  of  steam  exhausted. 

5.  The  form  of  the  jet  is  influenced  by  the  dimensions  of  the  chan- 
nels through  which  it  is  made  to  pass.     Under  ordinary  conditions,  it 
does  not  fill  the  stack  until  near  its  top.     If  the  diameter  of  the  stack 
is  changed,  that  of  the  jet  will  also  change. 

6.  All  portions  of  the  smoke-box  which  are  in  front  of  the  diaphragm 
have  substantially  the  same  pressure;    and,  consequently,  a  draft- 
gauge  attached  at  any  point  may  be  depended  upon  to  give  a  true 
reading. 


256  LOCOMOTIVE  PERFORMANCE. 

7.  The  resistance  which  is  offered  to  the  forward  movement  of  the 
air  and  gases  between  the  ash-pan  and  the  stack  may  be  divided  ap- 
proximately into  three  equal  parts  which  are :  First,  the  grate  and  the 
coal  upon  the  same;   second,  the  tubes;   and,  third,  the  diaphragm. 
It  is  significant  that  the  diaphragm  is  as  much  of  an  impediment  to 
draft  as  the  fire  upon  the  grate. 

8.  The  form  and  proportions  of  the  stack  for  best  results  are  not 
required  to  be  changed  when  the  operating  conditions  of  the  engine 
are  changed;  that  is,  a  stack  which  is  suitable  for  one  speed  is  good 
for  all  speeds,  and  a  stack  that  is  suitable  for  one  cut-off  is  good  for  all 
cut-offs.     In  future  experiments  of  draft  appliances,  therefore,  results 
obtained  from  a  single  speed  and  a  single  cut-off  should  be  deemed 
satisfactory. 

9.  Other  things  remaining  unchanged,  the  draft  varies  with  the 
weight  of  steam  exhausted  per  unit  of  time;  if  the  number  of  pounds 
of  steam  exhausted  per  minute  is  doubled,  the  draft,  as  measured  in 
inches  of  water,   is   doubled;    if   it   is    halved,   the   draft  value   is 
halved. 

10.  As  regards  the  form  of  outside  stacks,  either  straight  or  tapered 
may  be  used.     From  a  designer's  point  of  view,  the  tapered  is  the  more 
flexible:   that  is,  with  the  tapered  stack,  the  draft  is  less  affected  by 
slight  departures  from  standard  dimensions.     Incidental  reasons,  there- 
fore, make  the  tapered  form  preferable.     For  best  results  the  diameter 
of  a  given  straight  stack  should  be  greater  than  the  least  diameter 
of  a  tapered  stack  for  the  same  conditions. 

The  term  "tapered  stack  "  used  in  this  and  other  paragraphs  sig- 
nifies a  stack  having  its  least  diameter  or  choke  16J  inches  from  the 
bottom,  and  a  diameter  above  this  point  which  increases  at  the  rate  of 
2  inches  for  each  foot  in  length. 

11.  In  the  case  of  outside  stacks,  either  straight  or  tapered  in  form, 
the  height  is  an  important  element.     In  general,  the  higher  the  stack 
the  better  will  be  the  draft. 

12.  The  diameter  of  any  stack  designed  for  best  results  is  affected 
by  the  height  of  the  exhaust-nozzle.    As  the  nozzle  is  raised  the  diam- 
eter of  the  stack  must  be  reduced,  and  as  the  nozzle  is  lowered  the 
diameter  of  the  stack  must  be  increased. 

13.  The  diameter  of  a  straight  stack  designed  for  best  results  is 
affected  by  the  height  of  the  stack.    As  the  stack  height  is  increased, 
the  diameter  also  must  be  increased. 

14.  The  diameter  of  a  tapered  stack  designed  for  best  results,  as 


THE  FRONT  END.  257 

measured  at  the  choke,  is  not  required  to  be  changed  when  tne  stack 
height  is  changed. 

15.  The  precise  relation  between  the  diameter  of  front  end  and  the 
diameter  and  height  of  stack  for  best  results  is  expressed  by  equations 
as  follows  : 

For  straight  stacks  : 

When  the  exhaust-nozzle  is  below  the  center  line  of  the  boiler 


9/>  ......       (8) 

When  the  exhaust-nozzle  is  above  the  center  line  of  the  boiler 

d=  (.246  +  .00123#)D-.  19fc  .....  (9) 

When  the  exhaust-nozzle  is  on  the  center  line  h  is  equal  to  zero 
and  the  last  term  disappears,  and  there  remains 


(10) 
For  tapered  stacks: 

When  the  nozzle  is  below  the  center  line  of  the  boiler 

d  =  .25Z)  +  .16fc  ............     (11) 

When  the  nozzle  is  above  the  center  line  of  the  boiler 

d  =  .25D-.16/t  ...........     (12) 

When  the  nozzle  is  on  the  center  line  of  the  boiler  h  becomes  zero. 
and 

d=.25D  .............     (13) 

In  all  of  these  equations  d  is  the  diameter  of  the  stack  in  inches 
For  tapered  stacks  it  is  the  least  diameter  or  diameter  of  choke. 
H  is  the  height  of  stack  in  inches,  and  for  maximum  efficiency  should 
always  be  given  as  large  a  value  as  conditions  will  admit.  D  is  the 
diameter  of  the  front  end  of  the  boiler  in  inches,  and  h  the  distance 
between  the  center  line  of  the  boiler  and  the  top  of  the  exhaust-tip. 

122.  Later  Experiments.  —  The  preceding  paragraphs  present  an 
account  of  researches  upon  the  locomotive  front  end  up  to  and  in- 
cluding the  year  1902.  The  work  then  completed  left  unsettled 
several  important  questions,  namely,  the  best  proportions  for  and  the 


258  LOCOMOTIVE  PERFORMANCE. 

value  of  inside  stacks,  false  tops  within  the  front  end,  and  draft- 
pipes.  The  equations  which  had  resulted  from  the  previous  work 
were  assumed  to  have  been  of  general  application,  but  their  truth 
when  applied  to  locomotives  having  short  stacks  upon  boilers  of 
large  diameter  had  not  been  confirmed  by  direct  experiment.  Upon 
the  completion  of  the  work  already  described,  therefore,  the  American 
Railway  Master  Mechanics'  Association  appointed  a  committee  to 
co-operate  with  the  American  Engineer  and  Purdue  University  in 
doing  such  work  as  still  remained  in  determining  the  proper  pro- 
portions of  the  several  details  making  up  the  locomotive  front  end, 
and  to  raise  by  subscription  among  railroad  companies  the  funds 
needed  to  meet  the  expense  thereof.  The  following  is  abstracted 
from  the  final  report  of  this  committee :  * 

The  tests  were  made  in  connection  with  New  York  Central  loco- 
motive No.  3929  mounted  upon  the  Purdue  testing  plant.  The 
locomotive  was  of  the  Atlantic  type  having  21/'X26//  cylinders  and 
72"  drivers.  The  inside  diameter  of  the  smoke-box  was  74",  and 
the  height  of  its  normal  stack  29".  The  methods  followed  were 
similar  to  those  already  described. 

The  tests  of  outside  stacks  involved  a  height  of  29  inches,  this 
being  the  maximum  practicable  for  road  conditions  upon  the  loco- 
motive under  test.  Stacks  of  this  height  were  supplied  in  diameters 
ranging  from  15  to  25  inches  by  2-inch  steps.  In  these  tests  no 
draft-pipes  or  netting  were  employed  in  the  front  end;  the  dia- 
phragm and  exhaust-pipe  were  the  only  details  present.  Under 
these  conditions,  with  a  29-inch  height,  the  best  diameter  was  found 
to  be  23  inches,  though  this  was  not  much  better  than  that  of  21 
inches.  The  exact  arrangement  of  equipment  for  the  best  results 
is  shown  by  Fig.  148.  The  notation  under  this  figure  and  under 
those  which  immediately  follow  gives  the  draft  obtained  with  a 
constant  back  pressure  of  3.5  pounds.  It  will  hereafter  appear  that 
there  are  better  arrangements  than  that  shown  by  Fig.  148.  The 
point  which  is  proven  is  that,  assuming  a  plain  outside  stack  29 
inches  high  to  be  used,  its  diameter  for  best  results  is  23  inches,  as 
given. 

The  experiments  included  inside  stacks  of  four  different  diam- 
eters ranging  from  15  to  21  inches,  a  constant  outside  height  of 


*  The  report  in  full  will  be  found  in   the  Proceedings  of  the  Master  Mechanics' 
Association  for  June,  1906. 


THE  FRONT  END. 


259 


29  inches,  and  a  penetration  into  the  smoke-box  of  12,  24,  and 
36  inches,  respectively.  The  best  proportions  for  this  form  of 
stack  are  shown  by  Fig.  149  accompanying.  Its  diameter  is  21 
inches  and  its  penetration  into  the  smoke-box  is  12  inches.  Results 
of  nearly  the  same  value  were,  however,  obtained  with  stacks  of 
smaller  diameter  having  greater  penetration.  From  values  obtained 
it  appears  that  as  the  degree  of  penetration  increases  the  diameter 
of  stack  should  be  reduced.  The  effect  is,  in  fact,  of  the  same  nature 
and  degree  as  that  which  results  from  raising  the  exhaust-tip.  It 
is  noteworthy  also  that  these  values  for  the  plain  inside  stack  are 
not  materially  better  than  those  for  the  plain  outside  stack,  a  fact 
which  was  formulated  as  a  conclusion  resulting  from  the  work  of 
1902. 


DRAFT,  4.54 

FIG.  148. 


DRAFT,  4.71 

FIG.  149. 


DRAFT,  5.06 

FIG.  150. 


It  had  been  planned  to  fit  the  front  end  with  three  different  false 
tops  located  at  12,  24,  and  36  inches,  respectively,  from  the  top 
of  smoke-box,  but  the  presence  of  the  steam-pipes  made  it  difficult 
to  fit  the  12-inch  top,  and  as  a  consequence  only  those  of  25  and 
36  inches  drop  were  experimented  upon.  In  each  case  stacks 
of  different  diameters  were  used,  the  outside  height  being  always 
29  inches.  The  best  results  were  obtained  with  a  stack  17  inches 
in  diameter  having  a  penetration  of  24  inches,  all  as  shown  by  Fig.  150. 
The  draft  resulting  therefrom,  when  the  back  pressure  was  3.5  pounds, 
was  5.06.  In  all  cases  with  the  false  top  the  17-inch  stacks  gave 
best  results.  A  comparison  of  results  with  those  obtained  from  a 
plain  outside  stack  and  from  a  plain  inside  stack  shows  material 
improvement  in  draft  values. 

The  false  top  necessarily  interferes  with  free  access  into  the  front 
end,  which  fact  makes  it  desirable  that  a  way  be  found  in  which  to 
secure  the  results  derived  from  it  by  means  which  are  more  simple. 
It  was  suggested  that  experiments  be  made  to  determine  the  effect 
upon  the  plain  inside  stack  of  an  annular  ring  or  flange  which  might 


260 


LOCOMOTIVE  PERFORMANCE. 


be  considered  as  representing  a  portion  of  the  false  top.  Responding 
to  this  suggestion  rings  of  two  diameters  were  used  on  17-inch  and 
19-inch  stacks  having  a  penetration  of  24  inches.  It  was  found  that 
the  proportions  shown  by  Fig.  151  gave  substantially  the  same  results 
as  those  obtained  with  the  best  arrangement  of  false  top.  Believing 
that  the  results  thus  obtained  pointed  to  the  desirability  of  having 
a  broader  curve  at  the  base  of  the  stack  and  that  when  the  proper 
proportions  were  understood  the  best  results  would  be  obtained 
from  such  a  curved  surface,  the  17-inch  stack  was  fitted  with  a  bell 
to  which,  for  purposes  of  experimentation,  flanges  of  various  widths 
were  afterward  added,  with  the  result  that  those  proportions  which 
appear  in  Fig.  152  proved  most  satisfactory.  The  best  draft  with 
the  false  top  was  5.06,  with  the  ring  5.05,  and  with  the  bell  4.98— 
that  is,  these  three  arrangements  are  practically  on  an  equality 


^H         «f 
19  rf 


DRAFT,  5.05 

FIG.  151. 


DRAFT,  4.98 

FIG.  152. 


DRAFT,  4.55 

FIG.  153. 


DRAFT,  4.40 

FIG.  154. 


No  other  arrangements  were  experimented  upon  which  gave  higher 
draft  values  than  these. 

Draft-pipes  of  various  diameters,  adjusted  to  many  different 
vertical  positions,  were  tested  in  connection  with  plain  stacks  of  the 
several  diameters  available.  The  elaboration  of  this  phase  of  the 
work  was  very  extensive.  It  was  found  that  for  best  results  the 
presence  of  a  draft-pipe  requires  a  smaller  stack  than  would  be  used 
without  it,  but  that  no  possible  combination  of  single  draft-pipe 
and  stack  could  be  found  which  would  give  a  better  draft  than  could 
be -obtained  by  the  use  of  a  properly  proportioned  stack  without 
the  draft-pipe.  While  the  presence  of  a  draft-pipe  will  improve 
the  draft  when  the  stack  is  small,  it  will  not  do  so  when  the  stack 
is  sufficiently  large  to  serve  without  it.  The  best  proportion  and 
adjustment  of  single  draft-pipe  and  stack  are  shown  by  Fig.  153. 

Double  draft-pipes  of  various  diameters  and  lengths,  and  having 
many  different  positions  within  the  front  ends,  all  in  combination 
with  stacks  of  different  diameters,  were  included  in  the  experiments 


THE  FRONT  END. 


261 


with  results  which  justify  a  conclusion  similar  to  that  reached  with 
reference  to  single  draft-pipes.  Double  draft-pipes  make  a  small 
stack  workable,  They  cannot  serve  to  give  a  draft  equal  to  that 
which  may  be  obtained  without  them,  provided  the  plain  stack  is 
suitably  proportioned.  The  arrangements  and  proportions  giving 
the  best  results  are  those  shown  by  Fig.  154. 

A  suggestion  as  to  a  standard  front  end  is  presented  as  Fig.  155, 


BEST  ARRANGEMENT   OF  FRONT  END. 
FlG.   155. 

which,  with  the  following  equations  referring  thereto,  may  be  accepted 
as  a  summary  of  the  conclusions  to  be  drawn  from  all  experiments 
made. 

For  best  results  make  H  and  h  as  great  as  practicable.     Also 
make 

d=.2lD  +  .16h, (14) 

b  =  2d  or  .5D, 

P=.32Z), 


.22D. 


(15) 
(16) 
(17) 


CHAPTER  XII. 

SUPERHEATING  IN  THE  SMOKE-BOX.* 

123.  An  Experimental  Determination. — The  arrangement  of 
steam-piping  on  an  American  locomotive  constitutes  one  of  the  many 
ingenious  features  which  have  so  long  served  to  perpetuate  the  general 
characteristics  of  the  early  machine.  From  the  time  the  steam  leaves 
the  dome  of  the  boiler  until  it  comes  within  the  influence  of  the  cylin- 
ders, there  is  no  possible  chance  by  which  it  can  lose  any  of  its  heat, 
and  during  a  portion  of  its  course  it  actually  gains  heat.  The  arrange- 
ment as  a  system  of  piping  is  perfect.  To  a  limited  degree  the  pipe 
also  serves  as  one  element  of  a  superheater,  the  smoke-box  constituting 
the  other.  The  extent  of  the  drying  or  superheating  effect  upon  the 
steam,  which  results  from  having  the  T  head  and  the  two  branch  pipes 
within  the  smoke-box,  has  long  been  an  open  question.  Some  foreign 
designers,  evidently  regarding  the  thermal  gain  resulting  from  such 
an  arrangement  as  of  less  consequence  than  accessibility  of  parts,  have 
carried  the  pipe  connections  outside  of  the  smoke-box;  while  in  this 
country  at  least  one  designer,  not  satisfied  with  following  the  usual 
practice,  has  carefully  planned  the  form  of  his  piping  to  facilitate  the 
transmission  of  heat  through  its  walls.  To  throw  some  light  on  the 
extent  of  the  drying  or  the  superheating  effect  upon  the  steam  while 
passing  these  pipes  in  the  smoke-box,  a  careful  test  was  made  upon 
the  Purdue  University  experimental  locomotive. 

In  preparation  for  the  experiment  a  thermometer  was  inserted  in 
the  T  head  at  A  (Fig.  156),  another  in  the  middle  of  one  branch  of  the 
steam-pipe  at  B,  and  a  third  in  the  saddle  close  to  the  valve-box  at  C. 
The  locomotive  was  then  run  under  load  with  the  reverse-lever  for- 
ward and  the  throttle  only  partially  open,  the  drop  in  pressure  from  the 
boiler  to  the  pipe  caused  by  throttling  being  sufficient  to  superheat  all 
of  the  steam  as  it  expanded  from  the  pressure  of  the  boiler  to  that  of 

*  The  substance  of  this  chapter  was  contributed  to  the  Railway  Review,  July 
28,  1894. 

262 


SUPERHEATING  IN  THE  SMOKE-BOX. 


263 


the  pipe.  The  extent  of  the  superheating  of  steam  at  any  given  pres- 
sure is  determined  from  its  temperature  alone.  If,  in  the  case  under 
consideration,  the  steam  neither  received  nor  gave  up  heat  in  its  pas- 
sage of  the  pipe,  all  three  thermometers  would  show  the  same  tempera- 
ture. A  difference  in  the  reading  of  the  thermometers,  therefore,  must 
indicate  a  transmission  of  heat. 

The  conditions  of  each  test  were  maintained  for  a  half-hour  before 
any  observations  were  made;   the  thermometers  were  then  read  and 


FIG.  156. 

other  observations  taken  simultaneously,  at  five-minute  intervals,  for 
a  second  half-hour,  there  being  no  difficulty  in  maintaining  constant 
conditions.  As  affecting  the  reliability  of  results  it  should  be  said 
that  the  thermometers  used  had  a  range  of  from  100°  to  200°  C.,  and 
read  to  fifths  of  a  degree.  They  were  inserted  in  long  tubes,  and  at 
A  and  B  these  tubes  were  protected  by  allowing  steam  under  the  pres- 
sure of  the  pipe  to  flow  past  them.  Fig.  157  shows  the  arrangement 
used  at  A  for  obtaining  the  temperature  of  the  steam  in  the  T  head. 
A  similar  arrangement  was  used  at  B.  Before  the  tests  were  made  the 
thermometers  were  carefully  compared  by  exposing  them,  while  in  the 
identical  tubes  used  on  the  locomotive,  to  saturated  steam  of  about 
the  same  temperature  as  that  recorded  in  tlie  experiment.  The  read- 


264 


LOCOMOTIVE  PERFORMANCE. 


FIG.  157. 


SUPERHEATING  IN  THE  SMOKE-BOX.  265 

ing  of  one  was  accepted  as  standard,  and  the  errors  of  the  other  two 
determined.  Since  all  results  depend  upon  differences  of  temperature, 
a  slight  error  in  the  actual  temperature  was  not  considered  important. 
Only  the  corrected  readings  are  given. 

The  following  is  a  summary  of  results  for  one  of  the  tests: 

Pressure  of  steam  in  boiler  by  gauge 130  Ibs. 

Pressure  of  steam,  in  steam- pipe  by  gauge 70  Ibs. 

Temperature  of  saturated  steam  at  pressure  of  steam-pipe.  .  315.68°  F. 
ObservetTtemperature  of  steam  at  A,  Fig.  156  (at  T  head) .  335.30°  F. 
Observed  temperature  of  steam  at  B,  Fig.  156  (at  middle 

of  steam-pipe) 339.65°  F. 

Observed  temperature  of  steam  at  C,  Fig.  156  (at  saddle). .  .   327.81°  F. 

Observed  temperature  of  gases  in  smoke-box 700.00°  F. 

Increase   of  smoke-box   temperature   over   temperature   of 

steam  in  the  boiler 345.00°  F. 

Approximate  distance  from  A  to  D,  measured  along  center 

line  of  pipe 56  in. 

Size  of  branch  pipe,  inside 3  X  6  in. 

Thickness  of  walls f  in. 

Approximate  time  occupied  by  the  steam  in  passing  from 

A  to  C 0.1  sec. 

It  will  be  seen  that  the  temperature  of  the  steam  was  increased  4.4° 
in  passing  from  A  to  B,  which  is  equivalent  to  a  gain  of  8.8°  in  passing 
through  the  whole  length  of  the  branch  pipe.  The  transfer  of  a  quan- 
tity of  heat  represented  by  an  increase  of  8.8°  in  the  temperature  of 
superheated  steam  would  affect  moist  steam  by  increasing  its  dryness 
about  0.5  of  1  per  cent.  It  is  believed  that  for  the  engine  experimented 
upon,  this  approaches  the  maximum  benefit  which,  from  a  thermal 
point  of  view,  is  to  be  derived  from  having  the  pipes  inside  the  smoke- 
box. 

The  conditions  of  the  test  were  varied,  and  all  the  work  repeated 
several  times  with  the  same  general  result.  When  a  larger  quantity 
of  steam  passed  the  pipe,  the  smoke-box  temperature  and  the  total 
heat  transmitted  increased,  but  the  amount  of  heat  transmitted  per 
pound  of  steam  was  not  materially  changed.  The  figures  given  are 
from  the  test  which  showed  the  greatest  heating  effect. 

Enlarging  the  pipes  within  the  smoke-box  would  have  a  pronounced 
effect  in  increasing  the  action  herein  considered,  since  it  would  both 
add  to  the  extent  of  heating  surface  and  also  lengthen  the  time  occupied 
by  the  steam  in  passing  the  same;  but  as  a  practical  matter  a  limit  to 
such  enlargement  for  simple  engines  is  soon  reached.  It  therefore 
seems  unreasonable  to  expect  the  steam  to  be  dried  to  any  consider- 


266  LOCOMOTIVE  PERFORMANCE. 

able  extent  in  its  passage  of  the  smoke-box.  Nevertheless,  there  is 
some  gain,  and  a  little  gain  is  far  better  than  a  little  loss. 

It  is  likely  that  a  two-cylinder  compound  may  reap  some  material 
advantage  from  the  heat  transmitted  to  its  receiver,  for  in  this  case 
the  heating  surface  may  be  quite  extensive,  and  the  movement  of  the 
steam  through  the  receiver  comparatively  slow.  Moreover,  the  re- 
ceiver pressure  being  lower  than  the  pipe  pressure  of  a  simple  engine, 
there  is  a  greater  difference  of  temperature  between  the  smoke-box 
gases  and  the  steam. 

An  interesting  result  of  the  test  is  found  in  the  fact  that  the  ther- 
mometer in  the  saddle  at  C  indicated  a  temperature  7.5°  lower  than 
the  temperature  in  the  T  head  at  A,  and  16.3°  lower  than  the  presum- 
able temperature  at  the  lower  end  of  the  steam-pipe  at  D,  so  that, 
from  the  T  head  to  the  cylinder  the  steam  does  not  gain,  but  actually 
loses  heat.  This  effect  is  to  be  accounted  for  in  the  fact  that  the  mean 
temperature  within  the  cylinders  is  much  lower  than  the  temperature 
of  the  incoming  steam,  and  that  this,  combined  with  the  effect  of  radia- 
tion from  the  saddle,  operates  to  lower  the  temperature  of  the  iron 
which  surrounds  the  steam  in  its  course  through  the  saddle.  It  is  cer- 
tainly clear  that  the  heat  given  the  steam  by  the  smoke-box  is  soon 
taken  away  again  by  the  saddle,  but  how  much  of  this  cooling  effect  of 
the  saddle  is  due  to  radiation  is  not  shown.  Experience  with  station- 
ary engines  which  have  no  saddles,  however,  forbids  our  charging  it 
all  to  radiation. 


IV.   THE  ENGINES. 

CHAPTER  XIII. 

INDICATOR   WORK. 

124.  Concerning  Indicator  Work. — From  the  beginning  of  the 
investigations  of  the  locomotive  laboratory  the  importance  of  giving 
close  attention  to  the  work  of  the  indicators  employed  upon  the  loco  - 
motive  cylinders  was  recognized.  A  good  indicator,  if  well  cared  for 
and  intelligently  operated,  can  be  depended  upon  to  give  an  accurate 
record  of  the  changing  pressure  within  the  cylinder,  but  the  same  in- 
strument, if  neglected  or  if  carelessly  manipulated,  may  give  results 
which  are  worthless.  In  the  work  of  the  locomotive  laboratory 
it  was  sought  not  only  to  have  the  indicator  itself  in  good  condition, 
but  to  have  its  action  such  as  to  insure  a  high  degree  of  accuracy  in 
its  use.  The  reducing  mechanism  for  transmitting  the  motion  of  the 
piston  and  of  the  indicator-drum  is  shown  by  Fig.  158.  The  motion  of 
the  cross-head  is  transmitted  to  the  pendulum  A  through  a  pin  work- 
ing in  a  slot  of  the  lever.  Another  slot  in  this  lever,  near  its  fulcrum, 
receives  and  serves  to  drive  a  pin  mounting  a  roller  fixed  to  the  metal 
bar  B,  which  slides  hi  the  guides  CC.  The  phi  driving  the  lever  A 
and  the  pin  upon  the  bar  B,  which  is  driven  by  this  lever,  can  only 
move  in  lines  parallel  with  the  motion  of  the  cross-head.  As,  in  re- 
sponse to  the  motion  of  the  cross-head,  the  lever  A  assumes  its  various 
angular  positions,  the  leverage  with  which  the  driving-pin  acts  upon 
it  is  constantly  changing,  but  similar  changes  are  taking  place  in  the 
leverage  with  which  the  lever  A  acts  upon  the  pin  which  is  attached 
to  the  bar  B,  hence  the  ratio  of  the  two  arms  remains  constant,  or 
would  do  so  if  the  pin  and  the  rollers  which  they  bear  were  infinitely 
small.  The  actual  error  arises  from  the  measurable  diameter  of  these 
pins,  and  is  so  slight  as  to  be  of  no  practical  consequence.  The  pres- 
ence of  the  bar  B,  having  a  motion  precisely  similar  with  that  of  the 
piston  and  in  line  with  the  drum-sheave  of  the  indicator,  permits  the 
use  of  a  short  cord  connection  in  driving  the  latter.  Neatly  made 

267 


268 


LOCOMOTIVE  PERFORMANCE. 


blocks  of  wood  clamped  to  the  bar  B  serve  as  points  of  attachment  for 
the  indicator-cards,  separate  points  being  employed  for  each  indicator. 
The  connection  of  the  steam  end  of  the  indicator  with  the  cylinder 
also  was  designed  to  be  as  close  as  possible.  This  consists  of  a  3-inch 
length  of  f-inch  pipe  and  one  f-inch  by  J-inch  elbow,  the  smaller  end 
of  which  receives  the  indicator-cock. 

The  cards  obtained  by  means  of  this  equipment  were  at  once  seen 
to  be  strikingly  different  from  those  obtained  from  locomotives  upon 
the  road,  where  a  considerable  length  of  pipe  between  the  cylinder  and 
indicator  appears  to  be  absolutely  necessary.  The  cards  from  the 


FIG.  158. — Indicator  Rigging. 

laboratory  were  smoother  in  their  general  outline,  and  the  events  of 
the  stroke  were  much  more  clearly  marked  upon  them.  While  these 
differences  are  entirely  creditable  to  the  laboratory,  the  fact  that  they 
existed  gave  rise  to  numerous  inquiries.  Different  parties  were  found 
to  be  interested  in  comparing  cards  from  the  laboratory  with  those 
obtained  from  road  tests,  with  no  satisfactory  results.  As  an  aid  to 
the  interpretation  of  cards  obtained  upon  the  road,  therefore,  it  was 
determined  to  make  a  study  of  the  effect  of  an  indicator-pipe  upon  the 


INDICATOR  WORK. 


269 


form  of  the  cards.  The  results  of  this  study  are  of  sufficient  interest 
to  warrant  some  reference  to  them  in  this  connection,  though  the  fact 
should  be  borne  in  mind  that  all  indicator  work,  underlying  the  data 
of  succeeding  pages,  was  obtained  under  the  favorable  conditions  set 
forth  by  Fig.  158. 

125.  The  Effect  upon  the  Diagrams  of  Long  Pipe  Connections 
for  Steam-engine  Indicators. — Experiments  were  first  undertaken 
upon  the  locomotive  which  was  equipped  with  two  indicators,  as  shown 
by  Fig.  159.  One  of  these,  hereafter  referred  to  as  the  cylinder-indica- 
tor, wTas  mounted  upon  the  usual  close  connection;  the  other,  hereafter 
referred  to  as  the  pipe-indicator,  was  mounted  at  the  end  of  such  a 
length  of  f-inch  pipe  as  was  necessary  to  carry  the  indicator  to  the 


FIG.  159.  , 

top  of  the  steam-chest,  as  must  ordinarily  be  done  in  conducting  road 
tests.  The  pipe  was  approximately  3^  feet  long,  but  it  was  bent  to 
form  smooth  curves,  and  was  carefully  covered  throughout  its  entire 
length.  By  these  means  it  was  thought  that  the  interference  resulting 
from  the  presence  of  the  pipe  would  be  reduced  to  a  minimum.  It  was 
sought  not  to  exaggerate  differences  in  the  results  occurring  through 
the  presence  of  the  pipe,  but  rather  to  reduce  such  differences  to  mini- 
mum values. 

In  carrying  out  the  experiments  cards  were  taken  simultaneously 
from  both  indicators  at  various  speeds.  The  indicators  were  then  re- 
versed in  their  positions,  and  the  observations  repeated.  The  averages  of 
results  thus  obtained  were  employed  as  final  values.  A  comparison  of 
results  discloses  the  fact  that  the  events  of  the  stroke  (cut-off,  release, 
and  beginning  of  compression) ,  as  recorded  by  the  pipe-indicator,  were 
all  later  than  similar  events  as  recorded  by  the  cylinder-indicator.  The' 
cards  from  the  pipe-indicator  made  all  changes  of  pressure  appear  more 


270 


LOCOMOTIVE  PERFORMANCE. 


gradual  than  those  from  the  cylinder-indicator,  and  the  area  of  the 
card  from  the  pipe-indicator  was  greater.  Fig.  160  presents  two  cards 
taken  simultaneously  from  the  indicators  in  question  at  a  speed  of  50 
miles  an  hour,  and  Table  LVIII.  presents  the  differences  in  power  as 
obtained  from  the  two  indicators  for  all  speeds  between  25  and  35 
miles  an  hour. 

TABLE  LVIII. 
ERRORS  IN  M.E.P.  CAUSED  BY  PIPE  CONNECTION  SHOWN  IN  FIG.  159. 


Speed,  Miles  per  Hour. 

Speed,  Revolutions 
per  Minute. 

Excess  of  Power  shown  by  Pipe-indi- 
cator as  Compared  with  that  shown  by 
Cylinder-indicator  in  Per  Cent. 

25 

134 

1.5 

30 

161 

2.1 

35 

188 

2.9 

40 

215 

4.9 

45 

242 

8.4 

50 

269 

14.0 

55 

296 

17.2 

126.  Experiments  upon  a  Stationary  Engine. — The  significance 
of  the  results  described  in  the  preceding  paragraph  was  such  that  a 


FIG.  160. 

more  elaborate  process  01  experimentation  was  entered  upon.  As 
the  locomotive  was  not  well  adapted  to  the  purposes  in  hand,  the  ex- 
periments were  transferred  to  a  Buckeye  engine  having  a  cylinder  7f 


INDICATOR  WORK.  271 

inches  in  diameter  by  15  inches  stroke.  Since  a  description  of  these 
later  experiments  will  serve  to  enforce  conclusions  which  may  be  drawn 
from  those  already  described,  some  reference  to  them  in  this  connec- 
tion will  be  of  interest.* 

The  power  of  this  engine  was  absorbed  by  an  automatic  friction- 
brake,  by  means  of  which  a  very  constant  load  was  obtained.  The 
head  end  of  the  engine  cylinder  was  tapped  with  two  holes  (a  and  b, 
Fig.  161),  both  in  the  same  cross-section,  and  hence  equally  exposed 
to  the  action  of  the  steam  in  this  end  of  the  cylinder.  One  of  these 
holes  (a)  was  made  to  serve  for  the  indicator  A,  the  cock  of  which  was 
placed  as  close  to  the  cylinder  as  possible.  The  hole  b  was  made  to 
receive  one  end  of  a  U-shaped  pipe,  the  other  end  of  which  entered  a 
coupling  fixed  in  the  angle-plate  c.  The  cock  of  a  second  indicator, 
B,  was  screwed  to  this  coupling.  A  single  system  of  levers  supplied 
the  drum  motion  for  both  indicators.  The  pipe  fittings  were  all  half- 
inch.  .  A  right-and-left  coupling  at  d  allowed  the  U-shaped  section, 
dfb,  to  be  removed  at  will,  and  replaced  by  a  similar  section  of  different 
length.  Pipe  lengths  of  5,  10,  and  15  feet  were  used,  length  being 
measured  from  the  outside  of  the  cylinder  wall  to  the  end  of  the  coup- 
ling under  the  cock  of  the  pipe-indicator.  The  pipe  and  fittings  were 
covered  first  with  a  wrapping  of  asbestos  board,  next  with  three-eights 
of  an  inch  of  hair  felt,  and  finally  with  an  outside  wrapping  of  cloth. 
It  is  to  be  noted  that  the  bend  in  the  pipe  at  /  is  easy,  and  that  there 
is  a  continual  rise  in  the  pipe  in  its  course  from  the  cylinder  to  the 
indicator.  Both  indicators  were  always  well  warmed  before  cards 
were  taken.  A  gauge  between  the  throttle  and  the  valve-box  was  use- 
ful as  an  aid  in  securing  constant  pressure  within  the  latter.  In  the 
tests  herein  described,  however,  the  boiler  pressure  was  kept  constant, 
as  nearly  as  possible,  and  the  throttle  was  generally  fully  open. 

A  pair  of  new  Crosby  indicators  was  set  apart  for  this  work,  and 
while  it  will  be  shown  that  the  value  of  the  comparisons  which  were 
undertaken  is  not  dependent  upon  a  high  degree  of  individual  accuracy 
in  the  indicators,  these  instruments,  when  calibrated  under  steam,  gave 
results  which  were  nearly  identical. 

The  results,  which  are  presented  in  the  form  of  diagrams  (Figs. 
162  to  171),  were  obtained  in  the  following  manner: 

*  An  account  of  results  obtained  from  experiments  in  connection  with  the  Buck- 
eye engine  was  first  published  as  a  paper  before  the  American  Society  of  Mechanical 
Engineers,  "  The  Effect  upon  the  Diagrams  of  Long  Pipe  Connections  for  Steam- 
engine  Indicators,"  Proceedings  of  the  Society,  May,  1896. 


272 


LOCOMOTIVE  PERFORMANCE. 


INDICATOR  WORK.  273 

The  engine  having  been  run  for  a  considerable  period,  and  the 
desired  conditions  as  to  pressure,  speed,  and  cut-off  having  been 
obtained,  cards  were  taken  simultaneously  from  the  cylinder-  and  the 
pipe-indicator.  Two  pairs  of  cards  (i.e.,  two  from  cylinder  and  two 
from  pipe)  were  thus  taken  as  rapidly  as  convenient,  after  which  the 
position  of  the  indicators  was  reversed,  and  the  work  repeated.  There 
were  thus  obtained  four  cylinder-cards  and  four  pipe-cards,  one-half 
of  each  set  having  been  made  by  one  of  the  indicators,  and  one-half  by 
the  other.  Next,  by  the  use  of  closely  drawn  ordinates  the  eight 
cylinder-cards  were  averaged  and  combined  in  the  form  of  a  single  card, 
and  the  eight  pipe-cards  were  in  the  same  way  combined  to  form  a 
single  pipe-card.  The  two  typical  cards  thus  obtained,  superimposed 
as  in  Fig.  162,  constituted  the  record  of  the  test.  This  process  was 
repeated  for  each  of  the  several  conditions  under  which  tests  were  made. 
It  is  proper  to  add  that  the  accuracy  of  the  indicators  used,  and  the 
constancy  of  the  conditions  maintained,  were  such  as  to  make  each  card 
almost,  if  not  quite,  the  exact  duplicate  of  the  representative  of  its  set. 

The  diagrams  presented  are  full  sized,  the  spring  for  all  being  sixty 
pounds. 

127.  Different  Lengths  of  Pipe. — The  effects  produced  by  the  use 
of  pipes  between  the  indicator  and  the  engine  cylinder,  of  five,  ten, 
and  fifteen  feet  in  length,  are  shown  in  Figs.  162,  163,  and  164  respec- 
tively, the  speed,  steam  pressure,  and  cut-off  being  constant.  As 
noted  upon  the  figures,  the  full  outline  represents  the  cylinder-card, 
and  the  dotted  outline  the  pipe-card. 

It  would  seem  that,  under  the  conditions  stated,  the  form  of  cylin- 
der-cards in  the  figures  referred  to  should  be  nearly  the  same,  whereas 
the  figures  show  them  to  vary  considerably.  It  will  be  well  to  omit, 
for  the  present,  all  discussion  concerning  the  causes  of  these  differences, 
and  to  accept  the  cylinder-card  in  each  case  as  representing  the  true 
conditions  within  the  cylinder. 

By  reference  first  to  Fig.  162  it  will  be  seen  that  the  effect  of  a  five- 
foot  pipe  is  to  make  the  indicator  attached  to  it  a  little  tardy  in  its 
action.  Thus,  during  exhaust,  when  for  a  considerable  interval  of 
time  the  change  of  pressure  to  be  recorded  is  slight,  the  lines  from  the 
two  indicators  agree,  but  during  the  compression  which  follows  the 
loss  of  sensitiveness  in  the  pipe-indicator  is  made  evident  by  its  giving 
a  line  which  falls  below  the  corresponding  line  traced  by  the  cylinder- 
indicator.  Similarly,  during  admission  there  is  an  approximate  agree- 
ment, while  during  the  expansion  which  follows,  the  lagging  of  the 


274 


LOCOMOTIVE  PERFORMANCE. 


pipe-indicator  results  in  a  line  which  is  higher  than  the  expansion  line 
given  by  the  cylinder-indicator.     As  a  result  of  this  lagging  in  the 


FIVE  FOOT  PIPE 


FIG.  162. 


TEN  FOOT  PIPE 


\       Pipe  Card 

V  v^       Cylinder  Card' 


FIG.  163. 


FIFTEEN  FOOT  PIPE 


.    FIG.  164. 

.NOTE. — The  speed  (200  revolutions  per  minute),  the  steam  pressure  (80 
pounds),  and  the  cut-off  (approximately  J  stroke)  were  constant  for  all  dia- 
grams on  this  page. 

action  of  the  pipe-indicator,  its  card  is  in  error  in  the  location  and  cur- 
vature of  the  expansion  and  compression  curves;  also  in  the  location 
of  the  events  of  the  stroke,  and  in  the  area  which  it  presents.  The 


INDICATOR  WORK.  275 

speed  at  which  these  errors  are  shown  to  occur  is  moderate  (200  revolu- 
tions), and  the  length  of  pipe  attached  to  the  indicator  is  not  greater 
than  is  often  used.  • 

The  general  effect  of  a  ten-foot  length  of  pipe  (Fig.  163)  is  the  same 
as  that  of  the  shorter  length,  but  the  lagging  action  due  to  the  pipe 
is  more  pronounced,  and  all  errors  are  proportionately  greater.  In 
this  case,  also,  the  admission  and  exhaust  lines  fail  to  agree,  the  total 
range  of  pressure  recorded  upon  the  cards  being  less  than  the  range 
existing  in  the  cylinder. 

A  still  further  addition  to  the  length  of  the  pipe  brings  changes 
(Fig.  164)  into  the  form  of  the  pipe-card  diagram  which,  while  entirely 
in  harmony  with  those  already  discussed,  are  of  such  magnitude  that 
the  form  of  the  card  loses  some  of  its  characteristic  features.  The 
admission  and  expansion  lines  are  lower  and  the  exhaust  line  is  higher 
than  are  the  corresponding  lines  for  the  true  card.  Reference  to  Table 
LIX.  wills  how  that  while  cards  from  pipes  of  five  and  ten  feet  in  length 
present  an  area  greater  than  that  of  the  true  card,  the  card  in  question 
(Fig.  164)  from  a  fifteen-foot  length  of  pipe  makes  the  area  less. 

A  comparison  of  the  pipe-cards,  Figs.  162,  163,  and  164,  makes  it 
evident  that  a  pipe  of  suitable  length  would  result  in  a  diagram  some- 
what similar  in  form  to  that  shown  by  Fig.  165  and  a  pipe  still  longer 
would  give  a  card  which  would  be  represented  by  a  single  line,  as  AB, 
Fig.  165. 


FIG.  165. 

Various  numerical  results  from  Figs.  162,  163,  and  164  are  exhibited 
in  Table  LIX. 

It  is  true  that  the  lengths  of  some  of  the  pipes  experimented  with 
are  excessive  as  compared  with  those  commonly  used  for  the  connec- 
tion of  indicators,  but  this  fact  does  not  deprive  the  results  of  their 
significance.  If  pipes  of  fifteen,  ten,  and  five  feet  in  length  will  produce 
the  effects  shown  by  Figs.  162,  163,  and  164  respectively,  it  is  but 
reasonable  to  suppose  that  pipes  of  less  than  five  feet  in  length  will 
produce  some  effect.  And,  since  the  effect  of  a  five-foot  pipe  is  con- 
siderable, this  length  must  be  greatly  reduced  before  the  effect  ceases 
to  be  measurable. 


276  LOCOMOTIVE  PERFORMANCE. 

It  will  be  shown  later  that  differences  of  speed  have  less  effect  than 
would  be  supposed  in  modifying  the  form  of  the  pipe-card;  that,  even 
with  a  speed  as  low  as  100  revolutions  per  minute,  the  effect  of  the 
pipe  is  strikingly  apparent.  It  will  be  shown,  also,  that  the  point  of 
cut-off  chosen  for  the  whole  series  now  under  consideration  (Figs.  162, 
163,  and  164)  is  not  especially  favorable  for  showing  the  modifying 
effect  of  the  pipe.  These  considerations,  together  with  the  fact  that 
indicator-pipes  of  three  and  four  feet  in  length  are  not  uncommon,  all 
serve  to  emphasize  the  practical  value  of  the  effects  noted. 

128.  The  Form  of  the  Cylinder  Diagrams. — It  may  be  well  at  this 
point  to  consider  the  causes  tending  to  change  the  form  of  the  cylinder 
diagrams  as  they  appear  in  the  different  figures  (Figs.  162,  163,  and 
164),  and  to  consider  the  evidence  which  justifies  their  acceptance  as 
true  diagrams.  A  study  of  the  diagrams  and  data  will  make  it  evident 
that  the  differences  are  due  wholly  to  a  change  in  the  length  of  the 
pipe.  This  single  change,  however,  introduces  an  incidental  change 
(1)  in  the  clearance,  (2)  in  the  extent  of  surface  exposed  to  the  action 
of  the  steam,  and  (3)  in  the  velocity  of  flow  in  and  out  of  the  pipe  at 
the  point  of  its  connection  with  the  cylinder. 

The  effect  produced  by  the  several  pipes  upon  the  clearance  of  the 
engine  is  given  below: 

Cylinder  and  port  clearance,  per  cent  of  piston  displacement 4.08 

Clearance  due  to    5-ft.  pipe,    "       "     "       "              "            2.69 

"     "  10-ft.      "       "      "     "       "              "            5.14 

"     "  15-ft      "       "      "     "       "              "            7.84 

Total  clearance  with    5-ft.  pipe  in  place,  per  cent  of  piston  displacement 6.77 

"    10-ft.     "      "      "        "       "     "       "                "           9.22 

"    15-ft.     "      "      "        "       "     "       "                "           11.92 

The  area  of  surface  bounding  the  clearance  space  was  affected  by 
the  pipes  as  follows: 

Surface  bounding  clearance  space,  no  pipe  attached 131.4  sq.  in. 

"       when    5-ft.  pipe  was  in  place 250.2  "    " 

"     10-ft.     "       "     "      "    366.1   "    " 

"     15-ft.     "       "     "      "    486.0  "    " 

Increased  clearance  would  lower  the  pressure  at  the  end  of  com- 
pression, and  would  change  the  curvature  of  the  compression  line  but 
it  would  not  make  the  compression  line  as  it  appears  in  Fig.  164. 

The  larger  exposed  surface  would  increase  the  effect  due  to  the 
interchange  of  heat  between  the  steam  and  the  walls  inclosing  it.  If 
it  be  assumed  that,  during  the  early  stages  of  compression,  this  inter- 


INDICATOR  WORK.  277 

change  results  in  reevaporation,  and  during  the  later  stages  in  con- 
densation, the  sum  total  of  the  effect  would  be  in  line  with  that  re- 
corded. Such  an  assumption  is  reasonable,  and  such  an  action  may 
in  part  account  for  the  change  under  discussion,  but  its  extent  is 
not  likely  to  be  as  great  as  the  indicator  has  recorded. 

By  far  the  most  active  agent  tending  to  reduce  the  curved  com- 
pression line  of  Fig.  162  to  the  straight  line  of  Fig.  164  is  the 
movement  of  steam  hi  and  out  of  the  mouth  of  the  pipe.  Thus, 
when  compression  begins  in  the  cylinder,  the  pressure  at  the  end 
of  the  pipe  is  greater  than  that  in  the  cylinder  (see  Fig.  164),  and 
steam  must  flow  from  the  pipe  to  the  cylinder.  This  current  of  steam 
entering  the  cylinder  just  when  the  mixture  of  steam  and  water  already 
there  is  undergoing  the  early  stages  of  compression  helps  to  augment 
the  cylinder  pressure,  and  to  carry  the  early  part  of  the  compression 
line  higher  than  it  would  otherwise  go.  As  the  process  of  compression 
goes  on  the  current  hi  the  pipe  is  reversed,  and  the  cylinder  supplies 
steam  to  the  pipe,  thus  causing  the  curve  for  this  portion  of  the  event 
to  fall  lower  than  it  otherwise  would.  Increased  curvature  during  the 
early  stages  and  diminished  curvature  during  the  later  stages  result 
in  a  line  which  is  approximately  straight  (Fig.  164). 

Similar  reasoning  will  account  for  the  rapid  drop  in  pressure  after 
cut-off  (cylinder-card,  Fig.  164).  At  the  instant  of  cut-off  the  cylinder 
is  supplying  steam  to  the  pipe.  The  flow  is  rapid,  and  the  kinetic 
energy  of  the  steam  causes  it  to  pile  up  in  the  pipe;  and,  although  as 
the  stroke  advances  this  pressure  is  constantly  decreasing,  the  pipe 
continues  throughout  expansion  to  hold  a  higher  pressure  than  that 
contained  by  the  cylinder. 

It  is  obvious  that  the  pressure  is  not  the  same  at  the  two  ends  of 
the  pipe,  except  for  points  indicated  by  the  crossing  of  the  lines,  as  at 
a,  b,  and  c  (Fig.  164),  and  that  the  difference  of  pressure  shown  at 
other  points  is  quite  sufficient  to  account  for  the  pronounced  change 
in  the  cylinder  diagram  when  pipes  of  different  lengths  are  used.  The 
existence  of  these  differences  hi  the  form  of  the  cylinder  diagram  does 
not  in  any  way  affect  the  results  which  are  here  presented.  All 
cylinder-cards  may  be  accepted  as  true,  and  the  fact  that  they  are 
not  all  alike  does  not  diminish  their  value,  but  rather  emphasizes  the 
importance  of  this  whole  subject. 

129.  The  Effect  of  the  Pipe  at  Different  Speeds.— The  effects  thus 
far  discussed  are  those  recorded  for  a  constant  speed  of  200  revolu- 
tions per  minute.  In  considering  to  what  extent  changes  of  speed  will 


278 


LOCOMOTIVE  PERFORMANCE. 


modify  these  results,  reference  should  be  made  to  Figs.  166, 167,  and  168, 
which  give  a  series  of  results  involving  a  ten-foot  pipe  for  which  all  condi- 


tOO  REVOLUTIONS  PER  MINUTE 


FIG,  166. 


200  REVOLUTIONS  PER  MINUTE 


FIG.  167. 


25Q  REVOLUTIONS  PER  MINUTE 


PIG.  168. 


NOTE.     The  steam  pressure  (80  pounds),  the  length  of  pipe  (10  feet)  and  the 
cut-off  (approximately  |  stroke),  were  constant  for  all  diagrams  on  this  page. 

tions  were  constant  except  that  of  speed.  Numerical  comparisons  may 
be  made  from  Table  LIX.  It  will  be  seen  that  increase  of  speed  pro- 
duces modifications  in  the  form  of  the  pipe  diagrams  which,  in  kind, 


INDICATOR  WORK. 


279 


are  similar  to  those  produced  at  constant  speed  by  increasing  the 
length  of  the  pipe,  but  these  changes  are  not  great.  For  example, 
increasing  the  speed  from  100  to  200  revolutions  per  minute  (Figs. 
166  and  167)  produces  less  change  than  increasing  the  length  of  the 
pipe  from  five  to  ten  feet  (Figs.  162  and  163).  The  fact  that  an 
engine  runs  slowly,  therefore,  does  not  seem  to  justify  the  use  of  an 
indicator  at  the  end  of  a  considerable  length  of  pipe.  Slow  running 
reduces  the  error;  it  cannot  be  depended  upon  to  eliminate  it  entirely. 
130.  The  Effect  of  the  Pipe  at  Different  Cut-offs.— The  relative 
effect  of  the  pipe  when  the  cut-off  is  changed,  other  conditions  being 
constant,  is  shown  by  Figs.  169, 170,  and  171,  and  numerically  by  Table 
LIX .  It  will  be  seen  that  the  differences  of  pressure  recorded  during  ex- 
pansion by  the  two  indicators  (pipe  and  cylinder)  are  approximately  the 
same  for  all  cut-offs,  but  the  relative  effect  of  these  differences  upon 
the  area  of  the  diagram  is  most  pronounced  upon  the  smallest,  or 
shortest,  cut-off  card.  The  fact  that  in  Fig.  171  the  steam  line  on 
the  pipe-card  rises,  while  that  of  the  cylinder-card  declines,  consti- 
tutes a  good  illustration  of  the  slowness  with  which  the  pressure  in 
the  pipe  responds  to  that  in  the  cylinder. 

TABLE  LIX. 
THE  EFFECT  OF  A  PIPE  ON  THE  FORM  OF  INDICATOR  DIAGRAMS. 


Pressures 

Steam  Con- 

Apparent 
Cut-off. 

Excess  (  +  )  or  Deficiency  (  —  )  shown  by  Pipe 
Diagram. 

sumption  per 
Horse-power 
per  Hour. 

Excess  shown 

Excess  (  +  )  or 

1 

by  Pipe  Dia- 
gram. 

At  the 

Deficiency 
(  —  )  as  shown 

1 

At  Cut-off. 

At  Release. 

Beginning  of 
Compression. 

M.E.P. 

by  Pipe 
Diagram. 

1 

J3.S 

ts  ^  o 

• 

o 

• 

fl 

• 

a 

a 

d 

a| 

S°-§ 

| 

s 

1 

3 

T) 

s 

T3 

g 

s 

£-0 

(T° 

1 

3 

1 

1 

1 

I 

1 

& 

1 

I 

J 

3.0 

11.5 

-1.3 

T-    2.2 

0.0 

0.0 

-0.1 

-     5.6 

+  1.2 

+   3.7 

-  0.1 

-  0.5 

2 

6.8 

24.3 

-2.8 

-   4.8 

+  2.1 

+  18.0 

+  0.2 

+      9.2 

+  2.7 

+  8.5 

-   0.4 

-    1.7 

3 

10.0 

38.4 

-5.1 

-   9.8 

+  6.5 

+  57.7 

+  4.0 

+  200.0 

-1.5 

-   5.0 

+  11.7 

+  45.9 

4 

4.0 

16.6 

+  1.1 

+   2.0 

-0.5 

-   3.7 

+  0.1 

+     6.0 

+  3.0 

+   8.8 

-   2.0 

-   7.2 

5 

7.5 

27.7 

-2.8 

-   4.8 

+  2.1 

+  18.0 

+  0.2 

+      9.2 

+  2.2 

+   6.6 

-   0.4 

-    1.7 

6 

6.8 

26.7 

-3.0 

-   5.7 

+  2.3 

+  24.3 

-0.3 

-     9.0 

+  5.3 

+  18.7 

-    1.0 

-    4.2 

7 

3.3 

25.4 

+  3.5 

+   6.7 

0.0 

0.0 

0.0 

0.0 

+  6.5 

+  35.3 

+  11.5 

+  47.9 

8 

7.0 

25.9 

-2.8 

-   4.8 

+  2.1 

+  18.0 

+  0.2 

+      9.2 

+  4.2 

+  12.8 

-   0.4 

-    1.7 

9 

2.3 

6.5 

+  6.0 

+  10.3 

+  3.0 

+  18.2 

+  1.0 

+   50.0 

+  1.4 

+   3.4 

-   6.8 

-23.6 

All  percentage  values  are  based  on  results  from  cylinder  diagrams.  For  example,  in 
Test  No.  4  the  pressure  at  cut-off  shown  by  the  pipe-card  is  2  per  cent  in  excess  of  that  shown 
by  the  cylinder  or  true  card;  the  pressure  at  release  by  the  pipe;card  is  3.7  per  cent  less 
than  by  the  true  card;  the  pressure  at  the  beginning  of  compression  by  the  pipe-card  is  6 
per  cent  greater  than  by  the  true  card;  and  the  mean  effective  pressure  by  the  pipe-card 
is  8.8  per  cent  greater  than  by  the  true  card. 


280 


LOCOMOTIVE  PERFORMANCE. 


Comparisons  have  been  made  from  tests  run  under  still  other  con- 
ditions, and  all  conclusions  thus  reached  have  been  consistent  with 
those  presented.  This  whole  plan  of  work  was  outlined  with  the 


CUT-OFF  %  STROKE/ 


FIG.  169. 
CUT-OFF  J/4  STROKE 


FIG.  170. 

CUT-OFF  y%  STROKE 


PIPE  CARD 

CYLINDER  CARD 


FIG.  171. 

NOTE. — The  cut-off  as  given  above  is  approximate.  The  steam-pressure  (80 
pounds),  the  speed  (200  revolutions  per  minute)  and  the  length  of  pipe  (10  feet), 
were  constant  for  all  diagrams  on  this  page. 

expectation  of  securing  such  data  as  would  permit  a  complete  analysis 
of  the  effects  produced  by  a  pipe.  But  the  results  show  that  these 
effects  are  modified  by  so  many  different  conditions  that  their  precise 
character  cannot  be  safely  predicted.  Even  if  it  were  possible  to 


INDICATOR  WORK.  281 

construct  an  expression  for  reducing  a  distorted  pipe  diagram  to  a 
form  which  would  correctly  represent  the  relation  of  pressure  and 
volume  within  the  cylinder,  the  number  of  its  terms  would  be  so 
great,  and  its  form  so  complicated,  that  the  expression  would  have 
no  practical  value. 

131.  Conclusions. — The  following  conclusions  constitute  a  sum- 
mary of  the  data  already  presented : 

1.  If  an  indicator  is  to  be  relied  upon  to  give  a  true  record  of  the 
varying  pressures  and  volumes  within  an  engine  cylinder,  its  connec- 
tion therewith  must  be  direct  and  very  short. 

2.  Any  pipe  connection  between  an  indicator  and  an  engine  cylin- 
der is  likely  to  affect  the  action  of  the  indicator;  under  ordinary  con- 
ditions of  speed  and  pressure  a  very  short  length  of  pipe  may  produce 
a  measurable  effect  in  the  diagram,  and  a  length  of  three  feet  or  more 
may  be  sufficient  to  render  the  cards  valueless,  except  for  rough  or 
approximate  work. 

3.  In  general,  the  effect  of  the  pipe  is  to  retard  the  pencil  action 
of  the  indicator  attached  to  it. 

4.  Other  conditions  being  equal,  the  effects  produced  by  a  pipe 
between  an  indicator  and  an  engine  cylinder  become  more  pronounced 
as  the  speed  of  the  engine  is  increased. 

5.  Modifications  in  the  form  of  the  diagram  resulting  from  the 
presence  of  a  pipe  are  proportionally  greater  for  short  cut-off  cards 
than  for  those  of  longer  cut-off,  other  things  being  equal. 

6.  Events  of  the  stroke  (cut-off,  release,  beginning  of  compression) 
are  recorded  by  an  indicator  attached  to  a  pipe  later  than  the  actual 
occurrence  of  the  events  in  the  cylinder. 

7.  As  recorded  by  an  indicator  attached  to  a  pipe,  pressures  during 
the  greater  part  of  expansion  are  higher,  and  during  compression  are 
lower,  than  the  actual  pressures  existing  in  the  cylinder. 

8.  The  area  of  diagrams   made   by  an   indicator   attached  to  a 
pipe  may  be  greater  or  less  than  the  area  of  the  true  card,  depending 
upon  the  length  of  the  pipe;   for  lengths  such  as  are  ordinarily  used 
the  area  of  the  pipe-cards  will  be  greater  than  that  of  the  true  cards. 

9.  Within  limits  the  indicated  power  of  the  engine  is  increased 
by  increasing  the  length  of  the  indicator-pipe. 

10.  Conclusions   concerning   the   character  of   the   expansion  or 
compression  curves,  or  concerning  changes  in  the  quality  of  the  mix- 
ture in  the  cylinder  during  expansion  or  compression,  are  unreliable 
when  based  upon  cards  obtained  from  indicators  attached  to  the 
cylinder  through  the  medium  of  a  pipe,  even  though  the  pipe  is  short. 


CHAPTER  XIV. 
THE  EFFECT  OF  LEAD  UPON  LOCOMOTIVE  PERFORMANCE. 

132.  Lead. — When  a  valve  admits  steam  to  the  cylinder  before 
the  piston  has  completed  its  return  stroke  it  is  said  to  have  lead. 
The  amount  of  lead  is  the  width  the  steam-port  is  open  when  the 
engine-piston  is  at  the  beginning  of  its  stroke.  Speaking  in  very 
general  terms  it  may  be  said  that  the  effect  of  lead  is  to  admit  steam 
to  the  cylinder  before  the  piston  is  ready  to  start  on  its  forward  stroke. 
Its  presence  tends  to  insure  an  abundance  of  steam  behind  the  piston, 
at  the  very  beginning  of  the  stroke,  to  assist  in  the  maintenance  of  a 
satisfactory  supply  throughout  admission  and  to  promote  the  smooth 
running  of  machinery,  which  is  likely  otherwise  to  be  noisy.  Practice 
in  valve-setting  has  always  recognized  the  value  of  lead,  and  it  is  not 
often  that  an  engine  is  run  without  it. 

Any  admission  of  steam  behind  the  piston  before  it  has  completed 
its  return  stroke,  however,  results  in  negative  work,  and  for  this  reason 
the  amount  of  lead  should  not  be  excessive.  It  appears  reasonable 
to  assume  that  the  lead  should  at  all  times  be  such  as  will  insure  a 
complete  filling  of  the  clearance  space,  but  that  more  than  this  will 
affect  unfavorably  the  economic  performance  of  the  engine.  But  the 
amount  of  lead  necessary  to  give  this  result  can  only  be  determined 
by  the  use  of  the  indicator,  and  as  the  requirement  is  likely  to  vary 
with  changes  in  speed,  or  with  the  amount  of  compression  employed, 
the  'problem  is  not  a  simple  one. 

in  establishing  the  lead  for  the  valves  of  a  locomotive  it  is  usual 
to  make  the  measurements  when  the  reverse-lever  is  in  its  extreme 
position  This  determines  the  lead  for  the  maximum  valve  travel. 
Now,  it  happens  tnat  the  most  common  forms  of  locomotive  link- 
motion  give  an  increase  of  lead  as  the  cut-off  is  shortened.  Thus, 
with  a  T^-inch  lead  in  full  gear  a  valve  may  have  as  much  as  f-inch 
at  running  cut-off,  the  exact  amount  of  the  increase  depending  upon 

282 


EFFECT  OF  LEAD.  283 

the  proportions  01  the  individual  gear.  For  many  years  it  was  the 
practice  to  make  the  lead  in  full  gear  anywhere  from  ^  inch  to  J  inch, 
the  larger  amount  being  commonly  employed  upon  locomotives  in 
higher  speed  service.  These  amounts  give  satisfactory  action  when 
the  valve  is  at  full  travel,  and  for  a  long  period  the  practice  was  not 
questioned.  At  about  the  time  the  Purdue  testing-plant  came  into 
existence,  it  was  suggested  that  the  important  thing  was  to  have 
the  lead  satisfactory  for  the  running  cut-offs  rather  than  at  full  gear, 
and  that  this  should  be  accomplished  even  at  some  sacrifice  in  the 
distribution  for  other  cut-offs.  The  advent  of  the  Purdue  locomo- 
tive gave  some  opportunity  for  experiments  along  this  line. 

133.  Tests  Involving   Different  Amounts  of  Lead. — Locomotive 
Schenectady  No.  1,  as  received  from  its  builders,  was  found  to  have 
a  A-  inch  lead  for  the  full  travel  of   the  valve,  and  at  short  cut- 
off to  give  an  indicator-card  having  a  loop  at  the  initial  end.     As  the 
presence  of  such  a  loop  is  always  to  be  accepted  as  evidence  of  an 
excessive  lead  or  compression,  it  was  determined  to  change  the  setting 
of  the  valves  by  changing  the  position  of  the  "  go-ahead  "  eccentric 
on  the  axle  by  an  amount  sufficient  to  eliminate  the  loop.     Before 
proceeding  with  this,  however,  measurements  were  made  to  determine 
all  events  of  the  stroke,  and  four  tests  were  run  to  determine  the  per- 
formance of  the  engine.     The  change  was  then  made,  all  measure- 
ments retaken,  and  other  tests  were  run.     The  results  of  the  tests 
made  prior  to  the  change  are  given  in  Chapter  IV.  as  Series  V,  while 
those  obtained  after  the  change  constitute  Series  A.     The  A  setting 
was,  in  fact,  allowed   to  stand  for  all  subsequent  work  with  Sche- 
nectady No.  1,  except  in  the  case  of  Series  J  and  K.     The  tests  with 
which  the  present  discussion  is  immediately  concerned  are  eight  in 
number,  designated  as  follows: 

15-1-V  in  comparison  with  15-1 -A. 
25-1-V  "  "  "    25-1-A. 

35-1-V  "  "  "    35-1-A. 

55-1-V  "  "  "    55-1-A. 

134.  Effect  of  Lead  upon  the  Events  of  the  Stroke. — In  reducing 
the  lead,  the  "go-ahead  "  eccentric  was  moved  backward  a  distance 
of  about  J  inch,  as  measured  on  the  circumference  of  the  axle,  or 
through  an  angle  of  approximately  four  degrees.    The  lead  at  full 
gear,  which  previous  to  this  change  had  been  ^  inch,  was  in  this  man- 
ner reduced  to  zero.    To  secure  a  measure  of  the  effect  of  the  change 


284 


LOCOMOTIVE  PERFORMANCE. 


upon  the  events  of  the  stroke,  the  engine  was  run  at  low  speed  under 
a  heavy  load,  with  the  reverse-lever  in  each  of  the  several  notches 
from  the  center  to  the  extreme  forward  position,  for  a  half-hour, 
during  which  time  two  complete  sets  of  .ndica  tor-cards  were  taken. 
Cards  were  taken  at  low  speed  and  heavy  power,  defining  clearly  the 
events  of  the  stroke.  All  cards  obtained  by  the  process  described  were 
worked  up  to  show  the  per  cent  of  stroke  at  which  the  events  occurred, 
and  the  average  values  for  all  cards  taken  with  the  reverse-lever  in  a 
given  position  were  accepted  as  representing  the  events,  for  that  posi- 
tion. These  values  are  given  in  Table  LX.,  in  which  Series  V  repre- 
sents conditions  before  the  change,  and  Series  A  the  conditions  after 
the  change.  They  are  also  shown  graphically  by  Fig.  172. 

TABLE  LX. 

EVENTS  OF  STROKE  IN  PER  CENT  MEASURED  FROM  INDICATOR- 
*  CARDS. 


Ill 

Series  V. 

Series  A. 

l|2 

Admis- 
sion. 

Cut-off. 

Release. 

Com- 
pression. 

Admis- 
sion. 

Cut-off. 

Release. 

Com- 
pression. 

1 

5.04 

25.1 

67.6 

42.1 

3.25 

24.7 

71.1 

33.1 

2 

3.65 

33.3 

73.8 

31.7 

1.7 

33.7 

77.9 

28.6 

3 

2.6 

42.7 

78.6 

25.4 

1.16 

45 

81.6 

23.5 

4 

1.74 

51.4 

82.5 

20.8 

.69 

54.1 

85.7 

17.7 

5 

1.16 

59.3 

85.8 

17 

.41 

61.9 

89 

14.6 

6 

.74 

66 

88.5 

13.7 

.16 

69.8 

91 

11.2 

7 

.5 

71.6 

90.7 

10.8 

.1 

74.8 

93.1 

9.39 

8 

.21 

76.1 

92.6 

9.06 

.14 

79.3 

94.2 

7.5 

9 

.16 

79.8 

93.7 

7.45 

0 

82.9 

95.4 

6.04 

10 

.05 

83 

94.9 

6.12 

0 

84.1 

96.2 

5.5 

11 

0 

85.1 

95.8 

5.00 

0 

86.71 

97 

4.4 

12 

0 

87.3 

96.6 

4.19 

0 

88.56 

97.5 

3.87 

13 

0 

88.7 

97.2 

3.52 

0 

90.2 

98.0 

2.77 

14 

0 

90 

97.7 

3.02 

0 

91.3 

98.6 

2.19 

15 

0 

91.1 

98.1 

2.76 

0 

92.7 

98.9 

2.09 

It  will  be  seen  that  the  effect  of  the  change  in  valve-setting  is  to 
retard  all  the  events  of  the  stroke.  For  long  cut-offs  these  effects 
are  so  small  as  to  be  negligible,  but  as  the  cut-off  is  shortened  they 
increase  in  all  cases  except  with  reference  to  the  cut-off.  From  a 
purely  academic  point  of  view  these  effects  appear  to  be  advantageous. 
For  example,  with  a  given  cut-off  the  release  is  delayed,  thus  pro- 
longing the  expansion,  while  a  relatively  greater  delay  in  the  beginning 
of  compression  contributes  to  a  free  exhaust.  With  reference  to  admis- 


EFFECT   OF  LEAD. 


285 


sion,  it  appears  that  when  the  reverse-lever  is  well  forward  (tenth  to 
fifteenth  notch)  neither  the  original  lead  of  ^  inch  nor  the  absence  of 
it  have  a  sufficient  effect  on  the  admission  to  show  on  the  indicator. 
The  reason  for  this  is  probably  to  be  found  in  the  fact  that  at  long  cut- 
offs the  travel  of  the  valve  is  so  rapid,  when  the  piston  is  at  the  end 
of  its  stroke,  that  the  precise  time  when  the  port  opens  is  not  a  matter 
of  great  importance.  As  the  reverse-lever  is  moved  toward  the  center, 


AV 


Compression 


7 


Acl 


lission 


t-Off 


Relea 


10  20  30  40  50       '     60  70 

Per  Cent  of  Stroke 

FIG.  172.— Events  of  Stroke. 


90 


100 


however,  the  lead  increases,  and,  as  will  be  hereafter  shown,  the  maxi- 
mum port-opening  diminishes,  and  the  effect  of  the  lead  upon  admis- 
sion, both  relatively  and  actually,  is  increased. 

135.  Effect  of  Lead  upon  Valve-travel  and  Port-opening. — 
The  extent  of  the  valve  travel  for  the  several  positions  of  the  reverse- 
lever  was  determined  by  means  of  apparatus  shown  in  Fig.  173. 
This  consisted  of  a  stop  (a)  secured  to  the  valve-stem,  a  wooden 
straight-edge  (6)  secured  to  the  engine  frame  directly  above  and 
parallel  to  the  valve-stem,  and  a  try-square  (c)  with  a  blade  suffi- 
c'ently  long  to  have  contact  with  the  stop  as  it  moved  back  and  forth 
with  the  valve-stem.  With  the  locomotive  running  under  desired 
conditions  the  try-square  was  moved  on  the  straight-edge  till  the 


286 


LOCOMOTIVE  PERFORMANCE. 


stop  just  touched  it  at  one  end  of  its  stroke,  after  which  a  line  show- 
ing its  location  was  drawn  on  a  piece  of  paper  fastened  to  the  straight- 
edge. The  try-square  was  then  moved  to  the  other  end  of  the  straight- 
edge and  the  process  repeated,  after  which  the  actual  travel  of  the 


FIG.  173. 

valve  was  found  by  measuring  the  distance  between  the  two  lines 
and  subtracting  the  known  width  of  the  stop. 

The  average  port-opening  was  found  by  suotracting  twice  the 
outside  ^lap  of  the  valve  from  the  travel  of  the  valve  and  dividing 
by  two.  Table  LXI.  presents  the  record  of  valve  travel  and  the 
port-openings,  as  determined  in  this  way  for  each  position  of  the 
reverse-lever. 

TABLE  LXI. 

VALVE  TRAVEL  AND  PORT-OPENING. 
(From  Right  Cylinder  of  Locomotive. ) 


Valve  Travel,  Inches. 

Port-opening,  Inches. 

Notch 

Forward  of 
Center. 

Series  V. 

Series  A. 

Series  V. 

Series  A. 

1 

1.94 

1.88 

.22 

.19 

2 

2.04 

1.96 

.27 

.23 

3 

2.19 

2.13 

.34 

.31 

4 

2.37 

2.32 

.43 

.41 

5 

2.58 

2.54 

.54 

.32 

6 

2.72 

2.81 

.61 

.65 

7 

3.07 

3.06 

.78 

.78 

8 

3.35 

3.30 

.93 

.90 

9 

3.55 

3.62 

1.02 

1.06 

10 

3.94 

3.90 

1.22 

.20 

11 

4.28 

4.28 

1.39 

.39 

12 

4.59 

4.58 

1.54 

.54 

13 

4.90 

4.91 

1.70 

.70 

14 

5.22 

5.25 

1.86 

.87 

15 

5.57 

5.57 

2.03 

2.03 

EFFECT  OF  LEAD.  287 

An  examination  of  the  table  discloses  the  fact  that  at  short  cut- 
offs, when  the  lead  is  reduced,  the  valve  travel  and,  consequently, 
the  port-opening  are  also  reduced,  though  the  effect  in  these  particu- 
lars is  not  great.  The  table  is  perhaps  chiefly  of  interest  for  the 
actual  values  it  assigns  to  the  port-openings  for  the  different  positions 
of  the  reverse-lever.  A  moment's  consideration  will  show  that  the 
lead  at  short  cut-offs  does  not  need  to  be  great  to  equal  the  maximum 
port-opening,  in  which  case  the  maximum  opening  of  the  port  occurs 
before  the  piston  starts  on  its  stroke.  With  lead  at  short  cut-offs,  of 
a  quarter  of  an  inch  or  more,  it  is  evident  that  such  a  condition  does 
occur.  The  precise  manner  in  which  it  occurs  is  best  seen  from  the 
ellipse  (Fig.  191),  showing  the  relative  motion  of  the  valve  and 
piston. 

136.  Effect  of  Lead  upon  the  Form  of  Indicator-cards. — Repre- 
sentative cards  from  the  several  tests  are  reproduced  as  Fig.  174, 
and  have  already  been  referred  to.  As  previously  stated,  it  was  the 
purpose  in  changing  the  valve-setting  to  so  reduce  the  lead  that  the 
loop  which  appears  in  the  cards  of  Series  V  should  disappear.  The 
results  show  (cards  of  Series  A)  that  this  was  not  entirely  accom- 
plished, and  that  some  further  reduction  might  have  been  made  upon 
the  right-hand  side,  but  the  change  which  was  made  is  nevertheless 
significant  in  its  effect  upon  the  indicator-cards. 

First  to  be  noticed  is  the  smaller  size  of  the  cards  of  Series  A.  It 
is  clear  that  by  delaying  the  opening  of  the  port  the  amount  of  steam 
admitted  is  reduced  and  the  work  per  stroke  diminished.  It  must 
be  admitted,  also,  that  the  cards  of  Series  A  are  not  so  well  filled  out 
at  the  initial  end  as  are  those  of  Series  V,  and  that  they  are  not  so 
well  marked  by  the  events  of  the  stroke.  These  effects  are  shown 
by  Fig.  175,  in  which  the  dotted  outline  represents  a  card  taken  when 
the  lead  was  considerable,  and  the  full  line  a  card  taken  after  it  had 
been  reduced.  The  reduction  of  lead  effects  a  reduction  in  the  back- 
pressure losses,  but  it  also  reduces  the  positive  work  under  the  steam 
and  expansion  lines.  Judging  from  the  cards  alone  it  would  appear 
to  be  a  fair  question  as  to  whether  any  advantage  had  been  gained  by 
reducing  the  lead;  but  it  must  be  remembered  that  a  reduction  in  the 
size  of  a  card  does  not  necessarily  constitute  an  argument  against 
reduced  lead,  since  the  work  per  stroke  can  always  be  increased  by 
moving  forward  the  reverse-lever.  The  advisability  of  the  change  is 
rather  to  be  judged  by  the  amount  of  steam  consumed  per  unit  power, 
and  to  this  phase  of  the  matter  attention  will  now  be  given. 


SPEED  IN   MILES  PER  HOUR 


CO 


m 


CO 

m 


m 


EFFECT  OF  LEAD. 


289 


137.  Steam  Consumption. — The  steam  consumption  constitutes 
the  one  fact  which  finally  determines  the  usefulness  of  any  alteration 
in  steam  distribution.  The  results  of  tests,  as  set  forth  in  Table 


Pressure 


FIG.  175. 


LXII.  and  as  presented  graphically  by  Fig.  176,  show  conclusively 
that  the  reduction  in  lead  effected  a  reduction  in  the  amount  of  steam 
consumed.  It  is  often  assumed  that  high  speeds  admit  of  the  use  of 


Speed  -Miles  Per  Hour 


10  20  30  40 

FIG.  176. — Steam  Consumption. 


50 


more  lead  than  is  desirable  when  the  speed  is  low,  but  the  results  do 
not  confirm  such  an  assumption.  They  show  that  the  loss  arising 
from  excessive  lead  is  less  than  when  the  speed  is  lower,  but  they  do 
not  in  any  case  show  that  the  larger  lead  gives  the  greater  economy. 

From  the  standpoint  of  steam  consumption  per  indicated  horse- 
power, there  can  be  no  question  but  that  the  performance  of  the 
engine  was  improved  by  so  reducing  the  lead  as  to  entirely  remove 


290 


LOCOMOTIVE  PERFORMANCE. 


the  loop  from  the  initial  end  of  the  card.  The  change  appears  to  have 
been  justifiable,  even  though  it  resulted  in  making  the  initial  end  of 
the  indicator-card  somewhat  rounded  under  certain  conditions  of  run- 
ning (Fig.  174).  A  comparative  study  of  the  indicator-cards  and  the 
record  of  steam  consumption  will  be  found  profitable. 

TABLE  LXII. 
STEAM  CONSUMPTION. 


Steam  per  I.H.P. 

Speed,  Miles  per 
Hour. 

Approximate  Cut-off, 
Per  Cent. 

Series  V. 

Series  A 

15 

29.97 

28.92 

25 

28.78 

28.06 

35 

25 

27.27 

26.93 

55 

30.62 

30.64 

138.  Lead  and  Machine  Friction. — It  is  shown  elsewhere  (Chap- 
ter XIX.)  that  high  initial  pressure  is  attended  by  heavy  losses  between 
the  cylinder  and  the  draw-bar  in  the  form  of  machine  friction,  from 
which  it  is  fair  to  conclude  that  the  friction  was  greater  in  the  tests 
of  Series  V  than  in  those  of  Series  A.     If  this  were  actually  the  case, 
and  if  the  steam  consumption  per  draw-bar  horse-power  were  plotted, 
the  difference  between  the  two  series  would  be  greater  than  that  ob- 
tained by  basing  the  comparison  on  the  indicated  horse-power,  that 
is,  greater  than  represented  by  Fig.  176. 

139.  Conclusions. — Although    the  experiments    above  discussed 
are  somewhat  limited  in  scope,  the  results  justify  the  following  rather 
general  conclusions : 

1.  Lead  should  never  be  so  great  as  to  give  a  loop  at  the  initial 
end  of  the  indicator-card. 

2.  If  necessary  to  avoid  the  loop  at  running  cut-offs,  the  valves 
of  a  locomotive  should  be  set  with  no  lead,  and  even  with  negative 
lead  for  the  full-stroke  position  of  the  reverse-lever. 

3.  Locomotives  having  their  valves  set  with  no  lead  in  full  gear 
will  be  found  to  respond  to  the  throttle  promptly  under  starting  con- 
ditions.   The  valves  move  so  rapidly,  when  the  crank  is  passing  its 
center,  that  the  port  opening  will  be  liberal  before  the  piston  is  fairly 
started  on  its  stroke. 


CHAPTER  XV. 

THE  EFFECT  OF  OUTSIDE  LAP  UPON  LOCOMOTIVE  PERFORMANCE. 

140.  Outside  Lap. — The  term  "outside  lap/'  or  "steam  lap/'  re- 
fers to  the  amount  by  which  a  slide-valve  in  its  central  position  over- 
laps the  outside  edges  of  the  steam-ports.  Thus,  in  Fig.  177,  the  out- 
side lap  of  the  upper  valve  is  J  inch,  of  the  middle  valve,  1  inch,  and 
of  the  lower  valve,  1J  inch.  Perhaps  the  most  obvious  effect  of  in- 
creasing the  outside  lap  is  the  necessity  for  increased  valve  travel,  if 
the  cut-off  is  to  remain  unchanged.  A  casual  inspection  of  Fig.  177 
will  show  that  a  certain  movement  of  the  valve  with  f-inch  outside 
lap  may  be  sufficient  to  operate  the  engine,  and  yet,  when  applied  to 
the  valve  having  1^-inch  outside  lap,  prove  inadequate  to  open  the 
steam-ports. 

To  determine  the  effect  upon  the  power  and  efficiency  of  a  loco- 
motive of  different  amounts  of  outside  lap,  three  series  of  tests  were 
run,  designated  as  A,  K,  and  J  respectively.  The  slide-valves  em- 
ployed in  each  series  were  alike  in  every  respect,  except  as  to  the  out- 
side lap,  which  varied  as  follows : 

Series  A,  Outside  Lap J  inch 

"      K,      "          " 1       « 

"      J,        "  " 1J     " 

Fig.  177  shows  all  the  dimensions. 

No  change  was  made  in  the  setting  of  the  eccentric  or  in  any  other 
position  of  the  valve-gear,  when  one  valve  was  interchanged  for 
another  having  a  different  amount  of  outside  lap.  When  increased 
travel  was  necessary,  it  was  obtained  by  carrying  the  reverse-lever 
in  a  notch  further  from  the  center  of  the  quadrant.  It  was  sought  to 
have  tests  run  under  conditions  which  would  give  as  nearly  as  pos- 
sible identical  cut-offs.  This  result  was  not  perfectly  secured,  but 
the  degree  of  success  is  shown  by  Table  LXIIL,  giving  the  events  of 
the  stroke  as  obtained  from  the  indicator-cards. 

291 


292 


LOCOMOTIVE  PERFORMANCE. 


Series  A 

Outside  Lap  =*" 
Inside  Lap     =  &" 

15-9-A 

15-1-A 

35-1- A 

55-1-A 


Series  K 

Outside  Lap  =1 

Inside  Lap     =& 

15-1 1-K 

15-  2-K 

35-  2-K 


Series  J 

Outside  Lap 

Inside  Lap 

15-15-J 

15-  4-J 

35-  4r-J 


FIG.  177. 

TABLE  LXIII. 
EVENTS  OF  STROKE. 


Reverse- 

Actual  Events  of  Stroke. 

Approxi- 
mate 
Cut-off. 

Outside 
Lap, 
Inches. 

lever, 
Notches 
Forward 
of  Center. 

Cut-off, 

Release, 

Compres- 
sion, 

Admis- 
sion, 

Per  Cent. 

Per  Cent. 

Per  Cent. 

Per  Cenv 

One 

} 

1 

23.4 

65.9 

36.0 

4.3 

Quarter 

2 

26.3 

69.7 

32.8 

2.8 

li 

4 

23.3 

69.9 

31.6 

1.3 

Three 

i 

9 

82.5 

95.1 

5.7 

0 

Quarters 

i 

11 

79.5 

93.5 

7.1 

0 

i'i 

15 

69.4 

90.5 

10.1 

0 

EFFECT  OF  OUTSIDE  LAP.  293 

141.  Events  of  Stroke. — In  order  to  study  the  events  of  the  stroke 
in  more  detail  there  was  attached  to  the  engine  a  valve-motion  indi- 
cator, by  means  of  which  the  diagrams  were  made,  showing  the  relative 
motion  of  the  valve  and  piston.     An  analysis  of  one  of  these  valve- 
motion  diagrams  *  (Fig.  178)  which  as  presented  are  approximately 
one  fourth  their  full  size,  will  disclose  effects  resulting  from  increased 
outside  lap  as  follows:  The  rapidity  with  which  the  valve  opens  the 
steam-port  is  increased,  resulting  in  a  freer  admission.     The  range  of 
cut-off  is  decreased.    When  the  cut-off  is  short  the  exhaust  is  hastened, 
an  effect  which  diminishes  as  the  cut-off  is  lengthened,  and  may  dis- 
appear entirely  when  the  reverse-lever  is  in  an  extreme  position.    The 
amount  by  which  the  steam-port  is  opened  to  the  exhaust  is,  with 
short  cut-off,  increased,  the  extent  of  such  increase  being  approxi- 
mately equal  to  the  increase  in  the  outside  lap.     This  applies,  however, 
only  to  the  shorter  cut-offs  and  to  reasonably  small  outside  laps, 
since,  when  either  of  these  factors  becomes  large,  the  exhaust-port  of 
the  valve  overtravels  the  steam-port,  and  exposes  thereby  its  full 
width  beyond  .which  it  is  not  safe  to  go. 

142.  Changes  in  the  Form  of  Indicator-cards  Resulting  from 
Changes  in  Outside  Lap. — The  cards  for  the  several  tests,  as  actually 
obtained,  are  shown  by  Figs.  180,  181,  and  182.     Referring  to  those 
taken  at  a  speed  of  15  miles  an  hour  (Fig.  180),  it  will  be  seen  that, 
as  regards  cut-off,  they  are  nearly  identical,  but  differ  essentially  in 
other  respects.    The  cards  made  for  the  valves  of  greatest  lap  have 
a  higher  steam  line  and  lower  exhaust  and  compression  lines  than 
those  taken  when  the  laps  was  less.    The  result  is  a  card  of  greater 
breadth  at  the  initial  end,  and  of  greater  area  for  the  same  cut- 
off.   The  same  characteristics  are  to  be  seen  in  the  cards  taken  at 
35  miles  per  hour  (Fig.  181),  though  in  these  cards  it  is  noticeable 
that  the  cut-offs  are  not  quite  the  same,  that  for  which  the  valve  had 
1  inch  outside  lap  being  greater  than  for  the  other  two. 

Cards  representing  long  cut-off  (Fig.  182)  are  hardly  to  be  regarded 
as  comparable,  since,  owing  to  the  fact  that  the  reverse-lever  was  in 
its  extreme  forward  position,  the  cut-off  was  regularly  diminished  as 
the  lap  was  increased.  The  effect  noted,  therefore,  with  increase  in 
outside  lap,  is  influenced  by  the  corresponding  decrease  in  cut-off. 
Cards  are  nevertheless  given,  since  they  emphasize  the  fact  that  even 
with  the  outside  lap  as  great  as  1^  inches,  the  admission  is  prompt, 
and  the  steam  line  well  sustained,  when  the  reverse-lever  is  nearly  in 

*  For  a  detailed  description  of  a  valve-motion  diagram,  see  paragraph  154. 


294 


LOCOMOTIVE  PERFORMANCE. 


EFFECT  OF  OUTSIDE  LAP. 


295 


296  LOCOMOTIVE  PERFORMANCE. 

its  extreme  position.  The  lower  cards  of  this  set  (Fig.  182)  show  the 
longest  cut-off  which  can  be  secured  with  a  valve  of  the  proportions 
given.  They  well  illustrate  the  difficulty  of  getting,  in  connection 
with  large  outside  lap,  a  card  which  shall  be  full  at  both  ends,  a  very 
desirable  thing  in  locomotive  service. 

A  comparison  of  the  cards  of  Figs.  180,  181,  and  182  discloses  the 
general  effects  of  increasing  the  outside  lap,  or  these  may  be  more 
easily  judged  by  reference  to  Fig.  183,  which  is  to  be  regarded  as  a 
diagrammatic  representation  of  what  actually  takes  place.  In  this 
figure  the  full  line  is  the  normal  card,  such  as  may  result  from  f-inch 
outside  lap,  and  the  dotted  line  is  that  which  results  when  a  valve  is 
used  having  a  greater  amount  of  outside  lap.  When  the  cut-off 
remains  constant,  the  effect  upon  the  form  of  the  card  of  increasing 


FIG.  183. — Effect  of  Outside  Lap  on  the  Form  of  an  Indicator-card. 

the  outside  lap  is  to  raise  the  steam  and  expansion  lines  and  to 
lower  the  exhaust  and  compression  lines.  It  gives  a  freer  exhaust, 
but  it  reduces  the  possible  range  of  cut-off.  All  of  these  effects 
may  be  traced  in  the  actual  cards  (Figs.  180,  181,  and  182),  and 
are  what  we  should  expect  from  a  consideration  of  the  valve 
diagrams. 

143.  Power  Variation. — The  changes  in   power,  resulting  from 
changes  in  outside  lap,  are  not  of  great  importance,  since,  within 
limits,  the  power  is  at  all  times  under  the  control  of  the  engineer  who 
has  but  to  manipulate  the  reverse-lever  in  such  a  manner  as  to  serve 
his  purpose.     For  this  reason,  and  because  the  similar  cards  are  not 
identical  in  cut-off,  no  attempt  should  be  made  to  compare  numerical 
values  representing  M.E.P.  or  power. 

144.  Steam  Consumption. — Evidently  the  important  fact  is  that 
of  steam  consumption.     If  the  engine  is  more  efficient  under  one  con- 
dition of  lap  than  under  another,  the  argument  will  be  strong  in  favor 
of  adopting  that  condition.    The  steam  consumption,  as  shown  by 
the  several  tests,  is  shown  by  Table  LXIV. 


EFFECT  OF  OUTSIDE  LAP. 


297 


TABLE  LXIV. 

STEAM  CONSUMPTION. 


Speed,  Miles 
per  Hour. 

Approximate 
Cut-off,  Per  Cent 
of  Stroke. 

Actual  Cut-off, 
Per  Cent  of 
Stroke 

Outside  Lap, 
Inches. 

Steam  per 
I.H.R 
per  Hour. 

82.5 

i 

39.2 

15 

80 

79.5 

1 

37.8 

69.4 

li 

35.1 

23.4 

i 

28.9 

15 

25 

26.3 

i 

28.8 

23.3 

i* 

28.5 

23.4 

I 

26.9 

35 

25 

26.3 

i 

27.8 

23.3 

li 

26.8 

The  table  shows  a  gain  in  steam  consumption  with  increased 
outside  lap  while  running  at  slow  speed  and  long  cut-off,  but  in 
drawing  any  conclusions  it  must  be  borne  in  mind  that  as  the  lap  was 
increased  the  cut-off  was  materially  decreased,  a  fact  in  itself  sufficient 
to  account  for  the  better  economy.  At  running  cut-offs  and  at  ordi- 
nary speeds  there  seems  to  be  very  little  change  in  the  steam  con- 
sumption, whatever  the  lap. 

The  fact  that  any  increase  of  outside  lap  does  not  increase  the 
economy  of  the  engine,  while  it  does  materially  reduce  the  flexibility 
of  the  valve-gear  in  respect  to  range  of  cut-off,  is  sufficient  to  justify 
common  practice  which  makes  this  feature  of  the  locomotive  slide- 
valve  comparatively  small. 


CHAPTER  XVI. 

THE  EFFECT  UPON  LOCOMOTIVE  PERFORMANCE  OF  INSIDE 
CLEARANCE.* 

145.  Inside  Clearance. — A  slide-valve,  which  in  middle  position 
has  its  inside  edges  in  line  with  the  inside  edges  of  the  steam-ports, 
over  which  it  is  designed  to  travel,  has  neither  inside  lap  nor  inside 
clearance.  It  is  sometimes  referred  to  as  being  "line  and  line." 
When  the  valve  is  so  proportioned  as  to  allow  the  inside  edges  of 
the  valve  to  overlap  the  inside  edges  of  the  steam-ports  for  mid-posi- 
tion, then  the  valve  has  inside  lap;  while,  on  the  other  hand,  if  the 
inside  edges  of  the  valve  fail  to  cover  the  steam-ports,  the  valve  has 
inside  clearance.  Thus,  in  Fig.  184,  the  first  valve  shown  has  ^-inch 
inside  lap;  the  second,  ^-inch  inside  clearance;  and  the  third,  f-inch 
inside  clearance. 

The  effect  of  changing  a  valve  from  inside  lap  to  inside  clearance, 
other  things  remaining  unchanged,  is  to  hasten  release  and  to  delay 
compression,  and  hence  to  increase  the  interval  of  time  during  which 
the  exhaust-port  is  open.  It  also  increases  the  extent  of  exhaust- 
port  opening.  As  a  consequence  of  these  effects,  the  exhaust  is  made 
freer  and  back  pressure  is  reduced,  giving  an  advantage  in  the  operation 
of  the  engine,  which  is  greatly  desired,  and  which  would  be  accepted 

*  Acknowledgment  for  assistance  rendered  in  the  investigations  of  inside  clear- 
ance and  outside  lap  is  due  to  Messrs.  Halstead,  Robinson,  Ede,  and  Wilson,  who, 
while  students,  presented  the  facts  which  are  herein  summarized,  in  the  form  of  the 
following  theses: 

"The  Effect  of  Increased  Inside  Clearance  upon  the  Efficiency  of  Locomotive 
'  Schenectady,*  "  by  W.  G.  Halstead,  B.M.E.,  1897;  "  The  Effect  of  Increased  Out- 
side Lap  upon  the  Efficiency  of  Locomotive  '  Schenectady,' "  by  G.  P.  Robinson, 
B.M.E.,  1897;  "The  Effect  of  Changes  in  Inside  Clearance  upon  the  Efficiency  of 
Locomotive  'Schenectady  No.  1,'"  by  S.  S.  M.  Ede,  B.M.E.,  1903;  "The  Effect 
of  Changes  in  Valve  Proportion  upon  the  Efficiency  and  Power  of  Locomotive 
'  Schenectady  No.  1,'  "  by  A.  M.  Wilson,  M.E.,  1903. 

298 


EFFECT  OF  INSIDE  CLEARANCE. 


299 


without  question  if  it  were  not  for  the  assumption  that  loss  of  effi- 
ciency attends  the  earlier  exhaust.  Until  quite  recently  it  was  the 
practice  to  run  all  locomotives  with  a  small  amount  of  inside  lap, 
usually  A  of  an  inch.  With  the  advent  of  the  modern  engine,  how- 


Series  H 
Steam  Lap  %" 
Inside  Clearance 


Series  A 
Steam  Lap  J 
Inside  Lap 


Series  I" 
Steam  Lap  \"    . 
Inside  Clearance  %' 


FIG.  184. 

ever,  and  especially  in  response  to  a  demand  for  a  free-running  engine 
at  higher  speeds,  the  inside  lap  has  been  reduced,  and  in  some  cases 
an  J-inch  or  ^-inch  inside  clearance  has  been  employed.  But  as  to 
the  wisdom  of  such  practice  men  best  qualified  to  speak  have  differ- 
ences in  their  opinions. 

For  the  study  of  this  subject  three  valves  having  the  proportion 


300 


LOCOMOTIVE  PERFORMANCE. 


shown  by  the  three  views  of  Fig.  184  were  employed.  These  valves 
are  identical,  excepting  as  to  their  inside  dimensions.  Six  tests  were 
run  with  each  set  of  valves,  the  conditions  of  speed  and  cut-off  being 
those  which -are  set  forth  by  Fig.  185.  All  valves  were  tested  with 
the  same  setting,  the  position  of  eccentrics  and  reverse-lever  being 
identical  for  the  corresponding  tests  of  the  different  series.  The  tests 
of  each  series,  therefore,  were  made  duplicates  of  each  other,  except 
in  so  far  as  the  results  were  effected  by  the  changed  proportion  of  the 
valves.  We  may  now  consider  the  nature  and  extent  of  these  effects. 


55 


-35 


ga 


25       34       44 


Cut-off  it  — v 


Center  123456789 
Reverse  Lever  Notch— * 

FIG.  185.— Tests  Run. 


146.  Maximum   Opening   of   Steam-port   into   Exhaust.  —  For 

short  cut-offs  the  travel  of  the  valve  is  ordinarily  insufficient  to  open 
the  full  width  of  the  steam-port  into  the  exhaust.  In  such  cases 
cutting  the  valve  away  to  give  inside  clearance  increases  the  maxi- 
mum opening  into  the  exhaust  by  an  amount  equal  to  the  change. 
A  very  material  gain  in  exhaust-opening  may  thus  be  secured.  For 
example,  the  tests  which  were  run  with  the  reverse-lever  in  the  first 
notch  gave  a  cut-off  of  25  per  cent.  The  maximum  opening  of  the 
steam-port  into  exhaust  under  these  conditions  for  the  several  valves 
tested  were  as  follows: 


For  valve  having 


?"  inside  lap  (Series  A) f  "  = 

/'      ' '     clearance  (Series  H) 

\"      "          "          (Series  I) 


'/  _  24'' 
-32" 


EFFECT  OF  INSIDE  CLEARANCE.  301 

147. — Changes  in  the  Events  of  the  Stroke  Resulting  from  Inside 
Clearance.—  Release  and  beginning  of  compression  only  are  affected. 
The  changes  in  these,  with  changes  in  valve  clearance,  are  most  pro- 
nounced for  the  shorter  cut-offs.  Thus,  with  the  reverse-lever  in  the 
first  notch  forward  of  the  center  (cut-off,  25  per  cent),  the  relation 
between  clearance,  cut-off,  and  release  is  shown  by  Table  LXV. 

TABLE  LXV. 

EVENTS  OF  THE  STROKE,  CUT-OFF,  25  PER  CENT. 


Inside  Lap  or  Clearance,  Inches. 

Release,  Per  Cent  of 
Stroke. 

Beginning  of  Compres- 
sion, Per  Cent  of  Stroke 

TT2  lap 
^  clearance 
f  clearance 

71.1 
59.0 
49.4 

33.3 
23.9 
17.3 

The  table  shows  that  a  change  from  ,&"  inside  lap  to  &"  inside  clear- 
ance, a  total  change  of  J,  hastens  the  release  and  delays  the  beginning 
of  compression  by  approximately  10  per  cent;  this  for  short  cut-off. 
When  the  cut-off  is  lengthened,  and  the  travel  of  the  valve  is  thereby 
increased,  the  relative  effect  upon  the  events  of  the  stroke  of  slight 
changes  in  the  dimensions  of  the  valve  itself  becomes  less  pronounced. 

148.  Changes  in  the  Form  of  the  Indicator-card  Resulting  from 
Inside  Clearance. — Fig.  186  presents  cards  obtained  with  the  reverse- 
lever  in  the  first  notch  (25  per  cent  cut-off),  and  at  speeds  of  15,  35 
and  55  miles  an  hour.  The  full-lined  cards  (Series  A)  were  obtained 
in  connection  with  valves  having  ^"  inside  lap,  and  are  assumed  as 
a  basis  of  comparison.  The  dotted-lined  cards  on  the  left  (Series  H) 
were  obtained  with  &"  inside  clearance,  and  on  the  right  (Series  I), 
with  f"  inside  clearance.  Where  slight  variations  in  the  steam  pres- 
sure for  the  different  tests  have  appeared,  the  cards  of  Series  H 
and  I  have  been  reduced  to  equivalent  cards,  for  which  the  pressure 
at  cut-off  is  identical  with  that  of  the  corresponding  card  of  Series  A, 
thus  supplying  a  logical  basis  for  comparison.  Referring  to  Fig. 
186  it  appears,  first,  that  with  increased  inside  clearance,  the  earlier 
exhaust  effects  a  noticeable  reduction  in  the  area  of  the  card  under 
the  exhaust  line;  secondly,  that  the  wider  exhaust-port  opening  and 
the  later  exhaust  closure  are  responsible  for  a  significant  change  in 
the  location  and  form  of  the  compression  line,  effecting  a  material 
increase  in  the  area  of  the  card  over  the  same;  and,  third,  that  the 
reduced  compression  tends  to  diminish  the  maximum  height  of  the 


302 


LOCOMOTIVE  PERFORMANCE. 


card,  so  that,  as  valve  clearance  is  increased,  the  maximum  pressure 
is  reduced.  With  a  given  amount  of  valve  clearance  all  of  these 
effects  become  more  pronounced  as  the  speed  is  increased.  The  per 
cent  of  area  lost  under  the  exhaust  line  and  gained  over  the  corn- 


is  Miles  per  Hour 
(/'     81  Revolutions  per  Minute     ^ 


35  Miles  per  Hour 
189  Revolutions  per  Minute 


55  Miles  per  Hour 
297  Revolutions  per  Minute 


FIG.  186. — Effect  of  Inside  Clearance  on  the  Form  of  Indicator-cards. 

pression  line  respectively,  expressed  in  terms  of  the  area  of  the  full- 
lined  card,  is  as  given  in  Table  LXVI.  The  values  of  the  Table 
appear  to  justify  the  conclusion  that,  when  the  reverse-lever  is  in 
running  position,  the  loss  in  the  area  of  the  card,  even  at  slow  speeds, 
is  so  small  as  to  be  negligible,  whereas  for  all  but  the  slowest  speeds 
there  is  gain,  and  at  high  speed  the  gain  is  material. 

The  changes  in  the  form  of  the  cards  under  starting  conditions 
are  shown  by  Fig.  187,  in  which,  as  before,  the  full  line  represents  the 
card  taken  in  connection  with  the  valve  having  -fa"  inside  lap  (Series 
A),  and  the  dotted  lines  cards  representing  &"  and  \"  inside  clearance 


EFFECT  OF  INSIDE  CLEARANCE. 


303 


(Series  H  and  I  respectively).  These  cards  represent  the  tests  at  the 
ninth  notch  (cut-off,  80  per  cent)  and  a  speed  of  15  miles  an  hour. 
They  show  that  the  loss  of  area  at  the  ends  of  the  cards,  attending 
increase  of  clearance,  while  actually  large,  is  in  part  compensated 


H  „. 


d 

*// 


FIG.  187. — Effect  of  Inside  Clearance  Under  Starting  Conditions. 

for  by  the  lower  exhaust  line  and,  compared  with  the  area  of  the 
card,  is  after  all  small. 

TABLE  LXVI. 

REVERSE-LEVER   FIRST  NOTCH   FORWARD   OF  CENTER,  CUT-OFF, 
25%   OF   STROKE. 


Speed. 

Clearance, 
Inches. 

Area  Lost  by 
Early  Release 
in  Per  Cent. 

Area  Gained  by 
Reduced  Back 
Pressure  and 
Late  Compres- 
sion in  Per  Cent. 

Net  Gain  (  +  ) 

Miles. 

Revolutions 
per  Minute. 

or  Loss  (  —  ) 
in  Per  Cent. 

15 

81 

ft 

t 

3.5 

6.0 

2.5 
.5 

-1 
-5.5 

35 

188 

ft 

1 

3.5 
5.25 

12.75 
15.0 

+  9.25 
+  9.75 

55 

296 

ft 

t 

5.25 

8.75 

21.0 
48.25 

+  15.75 
+  39.25 

149.  The  Blowing  through  Effect. — The  fact  that  a  valve  having 
inside  clearance  opens  both  steam-ports  to  each  other  as  well  as  to 
the  exhaust-ports  (see  Fig.  184)  has  often  been  regarded  as  the  chief 
objection  to  its  use.  The  interval  of  time  during  which  the  two  ports 
are  in  communication  depends  not  only  upon  the  extent  of  the  clear- 
ance itself,  but  upon  the  travel  of  the  valve  and  the  speed  of  the 
engine.  An  increase  either  in  the  travel  of  the  valve  or  in  the  speed 
of  the  engine  diminishes  the  interval. 

It  is  important  to  note  also  that  the  intercommunication  of  the 
steam-ports  does  not  lead  to  losses  of  live  steam.  Throughout  the 
interval  during  which  the  two  steam-ports  are  in  communication 


304 


LOCOMOTIVE  PERFORMANCE. 


both  are  seeking  to  exhaust  steam.  The  only  effect,  therefore,  which 
can  result  from  the  so-called  blow-over  action  is  an  interference 
between  the  exhaust  from  one  end  of  the  cylinder  and  that  from  the 
other  end;  a  portion  of  the  steam  from  the  port  which  is  just  opening, 
having  a  higher  pressure  than  that  which  is  issuing  from  the  opposite 
port  which  has  been  longer  open,  follows  the  exhaust  cavity  of  the 
valve  and  enters  the  opposite  port,  from  which  steam  would  other- 
wise be  flowing  (Fig.  188).  With  this  understanding,  and  with  the 
expectation  of  seeing  the  interference  manifest  itself  by  a  rise  in  the 
exhaust  line,  we  may  now  examine  the  card  for  the  purpose  of  ascer- 
taining to  what  extent  such  action  really  occurs. 

Most  important,  of  course,  is  an  understanding  of  the  action  under 


FIG.  188. 

running  conditions,  the  cards  for  which  appear  as  Fig.  186.  Here, 
it  appears,  that  at  a  speed  of  15  miles  an  hour,  &"  clearance  produces 
no  noticeable  disturbance  of  the  exhaust  line,  but  when  the  clear- 
ance is  increased  to  f",  an  amount  in  excess  of  any  which  has 
thus  far  been  commonly  employed  in  locomotive  service,  a  decided 
hump  appears.  Thus,  referring  to  the  dotted  outline  representing 
this  condition,  the  exhaust-port  did  not  close  until  the  point  a  was 
reached,  the  sudden  rise  in  back  pressure  in  the  vicinity  of  b  being 
due  to  an  influx  of  steam  from  the  opposite  port  which  was  then 
exhausting.  This,  then,  is  the  blowing-through  effect.  Upon  the 
cards  representing  the  35-mile  tests,  the  effect  gives  to  the  exhaust 
line  only  a  wave-like  appearance;  and  when  the  speed  has  been 
increased  to  55  miles,  even  this,  as  a  distinct  characteristic  in  the 
form  of  the  card,  nearly  or  quite  disappears.  No  doubt,  however, 
the  action  does  take  place  even  at  the  higher  speed,  and  its  com- 
plete suppression  would  further  lower  the  later  part  of  the  exhaust 


EFFECT  OF  INSIDE  CLEARANCE.  305 

line  and  the  compression  line,  but  any  harmful  effect  upon  the  form 
of  the  card  is  entirely  lost  in  the  lower  sweep  of  the  line  which  marks 
the  freedom  of  the  exhaust  action  as  a  whole. 

Those  who  have  feared  serious  loss  in  the  effect  of  inside  clear- 
ance under  conditions  of  starting  will  be  reassured  by  reference  to 
Fig.  187.  As  would  be  expected,  the  effect  here  is  most  pronounced, 
but  with  the  long  cut-offs  it  occurs  so  near  the  end  of  the  stroke  that 
it  does  not  greatly  reduce  the  area  of  the  card.  Thus,  in  Fig.  187, 
in  the  dotted  diagrams,  the  rise  beginning  at  6,  near  the  end  of  the 
exhaust  line,  appears  to  be  compression.  That  it  is  not  the  result  of 
compression  must  be  apparent  when  it  is  remembered  that  increased 
clearance  delays  compression,  and  hence  the  exhaust  closure  for  the 
cards,  which  are  shown  dotted,  must  be  later  than  for  the  cards  which 
are  shown  full.  As  a  matter  of  fact  the  exhaust-ports  for  the  dotted 
cards  closed  at  the  points  c  and  d  respectively,  and  consequently 
most  of  the  rise  which  occurs  at  an  earlier  point  in  the  stroke  is  the 
result  of  steam  coming  from  the  opposite  steam-port.  Obviously  the 
exhaust  from  the  port  at  the  other  end  began  when  the  return 
stroke  for  the  end  under  consideration  had  reached  the  points  e  and  / 
respectively. 

The  conclusion  is,  therefore,  that  the  fact  that  inside  clearance 
places  the  two  ports  in  communication  is  not  significant  so  far  as  its 
effect  upon  the  form  of  the  card  is  concerned,  even  though  the  amount 
of  clearance  be  as  great  as  f".  When  the  cut-off  is  late  the  effect 
is  too  near  the  end  of  the  stroke  to  be  serious,  and  when  the  cut-off 
is  early,  it  is  of  moment  only  at  slow  speed,  and  even  then  the  increased 
area  of  port-opening  which  the  clearance  gives  serves  to  quickly  dis- 
sipate the  back  pressure  resulting  from  the  blow-over. 

150.  Mean  Effective  Pressure. — It  has  already  been  shown  that 
increasing  the  inside  clearance  will,  at  speed,  increase  the  area  of  the 
card,  or,  in  other  words,  the  mean  effective  pressure  and,  consequently, 
the  power  of  the  engine.  A  measure  of  such  increase  for  speeds  of  55 
miles  an  hour  with  the  reverse-lever  in  the  first  notch  (cut-off,  25  per 

cent)  is  as  follows: 

M.E.P. 

With  valve  having  •&"  inside  lap  (Test  55-1- A) 17. 56 

With  valve  having  A"  inside  clearance  (Test  55-1-H) 21.58 

With  valve  having  f "  inside  clearance  (Test  55-1-1) 23 . 68 

An  increase  in  mean  effective  pressure,  and,  consequently,  of  the 
power  of  the  engine  in  the  ratio  of  17.5  to  23.7,  or  more  than  30  per 


30(3  LOCOMOTIVE  PERFORMANCE. 

cent,  by  merely  cutting  out  the  inside  of  the  valve,  does,  in  fact,  con- 
stitute a  strong  argument  in  favor  of  a  more  general  clearance.  In 
urging  the  force  of  such  an  argument,  however,  it  should,  of  course, 
be  granted  that  such  increase  is  only  possible  at  high  speed;  but  it 
is  when  speeds  are  high  that  those  effects  which  are  obtainable  by 
means  of  increased  clearance  are  most  desired. 

While  the  conclusions  of  the  preceding  paragraphs  are  important 
and  true,  too  much  emphasis  should  not  be  given  card  areas.  The 
fact  that  clearance  helps  to  make  a  larger  card  is  but  a  part  of  the 
story,  for  the  effects  of  a  large  card  may  be  obtained  in  various  other 
ways,  as,  for  example,  by  a  change  in  the  position  of  the  reverse- 
lever.  For  this  reason  it  is  unfair  to  assume  that  any  device  or  expe- 
dient which  increases  the  card  is  justified. 

With  this  in  mind  may  be  noted  the  character  of  the  changes  in 
the  form  of  the  card  resulting  from  clearance.  The  maximum  pres- 
sure, the  back  pressure,  and  the  pressure  during  compression  are  all 
thereby  reduced.  Pressures  acting  upon  the  piston  are  practically 
nowhere  increased,  but,  on  the  other  hand,  for  the  most  part  reduced. 
In  other  words,  the  increase  in  effective  work  is  chiefly  the  result  of 
a  diminution  in  the  negative  work  of  the  cycle.  Herein  is  the  explana- 
tion of  the  fact,  which  all  experimenters  with  inside  clearance  have 
observed,  namely,  that  "it  makes  a  free-running  engine." 

But  the  test  by  which  any  apparatus,  or  system  of  adjustment, 
which  is  designed  to  improve  the  distribution  of  steam  within  an 
engine  cylinder  should  be  judged,  is  that  of  economy.  The  real  ques- 
tion is  whether  by  its  use  a  given  amount  of  power  can  be  obtained 
by  the  expenditure  of  a  smaller  amount  of  steam.  If  so  the  de- 
vice will  prove  economical,  and  will  also  raise  the  maximum  limit 
of  power  which  the  locomotive  can  deliver.  If  it  cannot  it  will  prove 
wasteful,  and  will  reduce  the  maximum  power  which  the  locomotive 
can  deliver.  The  effect,  therefore,  of  inside  clearance  on  steam  con- 
sumption is  a  matter  which  should  outweigh  other  considerations. 

151.  Steam  Consumption  as  Affected  by  Increased  Clearance.— 
A  detailed  statement  of  the  steam  consumption,  and  of  other  related 
facts  under  the  conditions  of  the  several  experiments,  is  set  forth  in 
full  in  Table  LXVIL,  while  a  summary  of  the  important  facts  is 
presented  as  Figs.  189  and  190.  Fig.  189  shows  the  steam  consumption 
of  the  engine  at  different  rates  of  speed,  and  proves  the  truth  of  the 
commonly  accepted  theory,  namely,  that  increased  inside  clearance 
results  in  loss  of  efficiency  at  low  speeds.  For  example,  changing  the 


EFFECT  OF  INSIDE  CLEARANCE. 


307 


inside  of  a  valve  from  &"  lap  to  &"  clearance  increases  the  steam 
consumption  at  15  miles  an  hour  one  pound  per  horse-power,  and  a 
further  increase  of  inside  clearance  to  f"  adds  three  pounds  to  the 
steam  consumption.  As  the  speed  is  increased,  however,  the  differ- 


35 
30 

1 
1- 

£ 

1 

h 

CC 

\ 

•v 

^s 

r>( 

j 

'Sv- 

^ 

"^-fc 

X 

) 

M 

^ 

-—» 
•*^, 



^s 

—  —. 

—  —  ^ 

""••*, 

n 

>- 
>= 

— 

^  — 

^ 

^ 

^»  • 
^^x 

«= 
^ 

^ 

3 

•—  — 

• 

-c 

>— 

^..•** 

& 

p;a> 

& 

1—  (' 

1 

1 

CUT-OFF  25  PER  CENT  OF  STROKE 
CURVE  C  INSIDE  CLEARANCE  f" 
"         B        «                  "               ^" 
•  »          A        »                  LAP          ^-" 

?15 

CQ 

'10 

10  20  30  40  50 

Speed-Miles  Per  Hour 

FIG.  189. — Inside  Clearance  and  Steam  Consumption. 


ence  in  steam  consumption  for  the  different  amounts  of  inside  clear- 
ance diminishes,  until  at  a  speed  of  50  miles  an  hour  (270  R.P.M.),  or 
thereabouts,  we  have  the  same  steam  consumption  for  all  cases.  For 
speeds  above  50  miles  an  hour  the  least  steam  consumption  attends 
the  use  of  the  greatest  amount  of  inside  clearance,  while  the  steam 


308 


LOCOMOTIVE  PERFORMANCE. 


consumption  for  the  valve  having  no  inside  clearance  increases  rap- 
idly, with  increase  of  speed  beyond  this  limit. 


Steam  per  T.R.P.  per  Hour-Pounds 

S  S  8  '  -8  88?  £ 

p 

/ 

£ 

/ 

/ 

y 

/ 

/ 

V 

/ 

/ 

^/ 

^ 

/ 

/ 

/ 

C(" 

X 

^^* 

^^ 

•^ 

/ 

/ 

s 

/ 

/ 

py 

x^ 

s 

/ 

• 

—   — 

/ 

A( 

X 

*>_ 

0 

—  ' 

x*' 

SPEED  15  MILES  PER.  HOUR 
CURVE  C  INSIDE  CLEARANCE  f 
"        B        «                   y            $' 
11         A       t*                 LAP        '£" 

40  60  80 

Cut-Off  in  Per  Cent  of  Stroke 


100 


FIG.  190. — Inside  Clearance  and  Steam  Consumption. 

It  has  usually  been  assumed  that  losses  incident  to  the  use  of 
inside  clearance  are  greatest  when  the  cut-off  is  longest,  but  the  curves 
of  Fig.  190  imply  that  this  is  not  true.  These  curves  represent  the 


EFFECT  OF  INSIDE  CLEARANCE 


309 


steam  consumption  at  a  constant  speed  of  15  miles  an  hour,  but  with 
cut-offs  varying  from  25  to  over -80  per  cent,  and  indicate  that, 
as  the  cut-offs  are  increased,  the  steam  consumption  under  all  con- 
ditions of  clearance  approaches  the  same  value.  This  tendency  is 
sufficiently  pronounced  to  justify  the  conclusion  that  the  losses  due 
to  clearance  are,  other  things  being  equal,  diminished  as  the  cut-off 
is  increased. 

TABLE  LXVII. 
STEAM  CONSUMPTION  AS  AFFECTED   BY  INSIDE   CLEARANCE. 


Speed,  Miles 
per  Hour. 

Cut-off,  Per 
Cent  of  Stroke. 

Inside  Lap, 
Inches. 

Inside  Clear- 
ance, Inches. 

Steam  per  H.P.H. 
Pounds. 

A 

33.34 

15 

80 

& 

33.92 

... 

f 

35.39 

A 

28.92 

15 

25 

:& 

30.03 

•  - 

f 

32.96 

•h 

.  . 

26.93 

35 

25 

& 

28.9 

f 

29.36 

•h 

30.61 

55 

25 

A 

29.72 

•',-  .4 

f 

29.38 

The  above  statement  embodies  a  fair  interpretation  of  the  tests 
under  consideration.  It  would  not  be  safe  to  generalize  therefrom 
to  the  extent  of  assuming  that  these  principles  may  be  applied  directly 
to  the  performance  of  all  engines,  though  they  may  properly  be  accepted 
as  an  indication  of  what  is  likely  to  occur  under  similar  conditions. 

In  this  connection  it  will  also  be  well  to  remember  that  the  range 
of  clearance  used  in  the  experiments  extends  far  beyond  the  amounts 
which  have  thus  far  been  used  in  practice.  Where  inside  clearance 
has  been  resorted  to  it  has  not  often  exceeded  J  inch,  whereas  in  these 
experiments  a  maximum  of  f  inch  was  employed.  In  view  of  this  fact 
it  is  of  special  interest  to  note  that  even  with  a  clearance  as  great  as 
the  latter  amount,  it  ceases  to  be  disadvantageous  when  the  speed 
of  the  locomotive  reaches  the  moderate  limit  of  50  miles  an  hour. 


CHAPTER  XVII. 

LOCOMOTIVE  VALVE-GEARS.* 

152.  The  Function  of  a  Valve-gear. — The  valve-gear  of  a  modern 
locomotive^  contends  with  conditions  which  are  difficult  to  meet.     It 
is  designed  to  so  move  the  valve  it  drives  as  to  open  the  port  by  an 
amount  which,  at  running  cut-off,  usually  does  not  exceed  three- 
eighths  of  an  inch,  and  at  speed  the  entire  interval  during  which  any 
port  is  open  is  less  than 'a  twentieth  of  a  second.     If  normal  steam 
distribution  is  to  be  maintained  the  valve   must  move  with  great 
precision,  since  even  a  slight  change  in  the  extent  of  its  travel,  or  in 
the  time  of  its  action,  becomes  relatively  large  when  measured  by  the 
small  port  opening  and  the  brief  interval  during  which  the  port  is 
open.     Moreover,  a  valve  of  a  modern  locomotive,  weighing  with  its 
yoke  150  pounds  or  more,  requires  the  application  of  forces  of  con- 
siderable magnitude  to  give  it  motion,  and  its  action  involves  more 
than  ten  reversals  in  its  motion  each  second.     It  is  necessary  that  the 
gear  which  actuates  such  a  valve  be  free  from  lost  motion,  and  that 
it  be  so  stiff  as  to  admit  of  no  deformation  of  its  parts.     With  this 
understanding  of  the  requirement,  we  shall  do  well  first  to  examine 
that  type  of  valve-gear  which  is  common  in  American  practice,  and 
to  review  briefly  its  merits  and  defects. 

153.  A  Stephenson  Valve-gear,  which  is  so  familiar  to  all  that  it 
need  not  be  illustrated,  as  designed  to  drive  a  flat  valve,  contains  ten 
joints  having  motion  when  the  gear  is  in  action,  between  the  axle  and 
the  valve-yoke.     Lost  motion  in  any  of  these  will  modify  the  valve 
action.    Accurate  fitting  and  the  use  of  case-hardened  parts  have, 
however,  made  the  joint  of  the  link  motion  reasonably  satisfactory,  but 
the  average  gear  leaves  much  to  be  desired  in  the  way  of  stiffness.     It 
is  true  that  great  progress  has  been  made  in  this  latter  respect.     The 

*  Adapted    from  a  paper    before    the    Southern  &  Southwestern    Railway  Club, 
January,  1905. 

310 


LOCOMOTIVE  VALVE-GEARS.  311 

modern  engine  does  not  slow  down  when  the  throttle-opening  is 
increased,  as  used  sometimes  to  be  the  case  with  locomotives  having 
bent  and  limber  eccentric  blades;  but  even  in  the  modern  locomotive 
the  spring  of  parts  has  not  been  entirely  eliminated.  This,  however, 
may  be  greatly  reduced  by  the  adoption  of  the  marine  type  of  link, 
with  double  hangers,  giving  support  to  the  link  upon  both  sides,  and 
having  connection  with  a  very  heavy  reverse-shaft  and  -arms. 

154.  What  the  Stephenson  Gear  Does. — The  motion  communi- 
cated to  the  valve  by  the  Stephenson  gear  is  one  which,  beginning 
from  rest,  increases  to  a  maximum  and  then  gradually  diminishes, 
until  at  the  end  of  its  travel  it  comes  to  rest  again.  The  fact  that 
it  approaches  its  point  of  rest,  and  upon  reversal  recedes  therefrom 
with  a  relatively  slow  motion,  permits  the  valve  to  be  controlled  in 
its  course  more  easily  than  would  be  the  case  if  its  changes  in  velocity 
were  in  obedience  to  a  more  complicated  law.  The  gradual  change 
in  its  rate  of  motion  may  well  be  seen  in  a  curve  representing  the 
relative  movement  of  valve  and  piston  (Fig.  191). 

In  the  diagram  of  this  figure,  which  is  sometimes  referred  to  as  a 
valve  ellipse,  horizontal  distances  represent  piston  displacement, 
and  vertical  distances  valve  displacement.  The  figure  shows  two 
ellipses  corresponding  with  two  different  positions  of  the  reverse- 
lever.  The  distance  between  the  mid-position  line  and  the  upper  por- 
tion of  either  curve  indicates  the  distance  which  the  valve  is  re- 
moved from  its  central  position,  and  distances  along  the  mid-position 
line  represent  piston  displacement.  Thus,  in  the  original  diagram  from 
which  Fig.  191  was  made,  the  distance  along  the  line  AB,  from  the 
center  line  to  the  curve  c,  is  one  and  three-fourths  inches.  If  we 
subtract  the  outside  lap  of  the  valve  from  this  distance  the  result 
will  be  the  port-opening.  For  example,  in  the  present  case,  the  out- 
side lap  is  one  and  one-half  inches,  and  the  port-opening  on  the 
line  AB  is  one-fourth  inch.  In  the  particular  case  in  question 
the  shaded  area  represents  both  the  portion  of  the  stroke  and  extent 
of  the  port-opening.  As  many  valve  ellipses  can  be  made  as  there 
are  notches  in  the  quadrant  holding  the  reverse-lever.  Again,  while 
only  the  steam-port  opening  has  been  referred  to,  it  should  be  evi- 
dent, since  the  displacement  of  both  valve  and  piston  are  shown, 
that  the  time  and  extent  of  the  exhaust-port  opening  can  be  deter- 
mined as  well-  as  that  of  the  steam-port. 

155.  Devices  for  Increasing  the  Acceleration  of  the  Valve. — 
The  present  purpose  is  less  concerned  with  questions  of  port-opening 


312 


LOCOMOTIVE  PERFORMANCE. 


than  with  the  form  of  the  curve  representing  the  motion  of  the  vaive, 
for  it  will  be  well  at  this  point  to  discuss  briefly  certain  modifications 
of  existing  gears  designed  to  accelerate  the  valve  motion  when  the 
piston  is  at  the  end  of  its  stroke.  It  is  the  purpose  of  this  class  of  de- 
vice to  secure  a  quick  and  liberal  opening  of  the  port,  to  hold  the  valve 
nearly  stationary  during  admission,  and  to  close  the  port  promptly 
at  cut-off.  The  mechanical  arrangements  for  securing  these  results 
usually  consist  in  the  addition  of  mechanism  to  existing  valve-gears. 
A  number  of  different  gears  have  from  time  to  time  been  proposed 
and  used.  While  the  means  employed  vary  greatly  in  different  gears 
the  form  of  the  valve  diagram  will  be  much  the  same  for  all.  In  con- 
trast with  that  shown  by  Fig.  191,  it  will  be  a  figure  having  the  same 


FIG.  191. — Valve-motion  Diagram. 

total  length  and  the  same  total  width,  but  with  ends  much  flatter 
indicating  the  higher  velocities  of  the  valve  on  either  side  of  its  points 
of  reversal.  It  is  evident  that  increased  acceleration  requires  a  gear 
which  is  stiffer  than  that  which  is  usually  employed.  This  fact, 
together  with  a  knowledge  of  the  care  which  must  be  exercised  in  the 
construction  and  maintenance  of  normal  gears,  suggests  some  of  the 
difficulties  to  be  met  in  designing  and  maintaining  any  of  these  accel- 
erating devices.  The  conception  underlying  the  accelerated  device  is 
good,  but  the  locomotive  is  an  extremely  difficult  type  of  engine  upon 
which  to  employ  it.  The  fact  that  in  locomotive  service  the  valve 
travel  is  considerable,  and  the  speeds  are  oftentimes  enormously  high, 
makes  it  difficult  to  say  just  how  far  a  design  may  be  carried  to  secure 
such  stiffness  of  gear  and  increase  of  wearing  surfaces  as  may  be 
required  to  perform  the  work  imposed  by  any  of  the  devices  in  question. 
156.  Wiredrawing  as  a  Factor  Controlling  Valve-gear  Design. — 
Another  point  to  be  emphasized  in  connection  with  the  valve  ellipse 
is  the  small  extent  of  port-opening.  The  smaller  of  the  two  ellipses 
shown  represents  a  cut-off  of  20  per  cent  of  stroke.  The  greatest 
width  of  the  shaded  portion  on  a  full-sized  diagram  is  one-fourth  inch, 
which  is  the  maximum  steam-port  opening  at  this  cut-off. 


LOCOMOTIVE  VALVE-GEARS.  313 

It  is  commonly  assumed  that  all  wiredrawing  in  locomotive  ser- 
vice is  objectionable,  whereas,  there  is  one  very  useful  service  which 
it  renders.  It  is  that  of  assisting  in  the  maintenance  of  uniform 
conditions  upon  the  boiler  while  the  engine  is  operating  under  widely 
varying  conditions  of  speed.  The  significance  of  this  statement  will 
appear  if  we  assume  an  engine  at  a  speed  of  20  miles  an  hour,  with 
reverse-lever  and  throttle  set  to  create  a  demand  for  steam  such  as 
will  put  a  fair  working  load  on  the  boiler.  If  now,  by  a  change  in 
grade,  the  load  is  diminished  sufficiently  to  permit  the  speed  to  increase 
to  40,  50,  or  even  60  miles  an  hour,  it  will  generally  not  be  necessary 
to  change  the  reverse-lever  or  the  throttle,  the  wiredrawing  action 
coming  into  play  to  prevent  the  cylinder  from  taking  from  the  boiler 
more  steam  than  it  can  supply,  the  engine  meanwhile  continuing  at 
all  speeds  to  work  at  or  near  its  maximum  capacity.  This  automatic 
regulation  of  power  through  wiredrawing  is  one  which  means  much, 
both  as  a  matter  of  convenience  in  the  operation  of  the  locomotive 
and  as  a  factor  affecting  boiler  repairs. 

But  there  are  objections  to  wiredrawing  which  are  real  and  some- 
times serious,  arising  from  the  fact  that  as  the  process  proceeds  the 
cylinder  action  becomes  less  efficient.  The  loss  on  this  account  is, 
however,  smaller  than  is  generally  supposed.  Its  value  may  be  seen 
in  the  data  of  Chapter  V.,  or  better,  perhaps,  in  a  brief  summary  of 
facts  derived  from  a  locomotive  carrying  200  pounds  steam  pressure, 
which  is  as  follows: 


Speed  50,  steam  per  I.H.P.H.,  24.9 
"      40,      "        ll   I.H.P.H.,  23.7 


i  ( 


30,      ll        "   I.H.P.H.,  24.6 
20,      "        "   I.H.P.H.,  25.4 


These  values  correspond  with  the  cards  of  Fig.  192  for  the  28  per  cent 
cut-off. 

Results  for  other  cut-offs  are  substantially  the  same.  At  60  miles 
an  hour,  were  the  data  available,  the  consumption  would  probably 
rise  to  27  pounds.  It  is  a  principle  in  steam  engineering  that,  other 
things  remaining  the  same,  the  steam  consumption  should  diminish 
with  increase  of  speed.  This  principle  would  apply  in  locomotive 
service  were  it  not  for  the  fact  that  with  each  increment  of  speed 
there  is  a  change  in  the  distribution  of  steam.  The  result  is  that 
while  the  steam  consumption  diminishes  until  a  speed  of  35  or  40 
miles  an  hour  is  reached,  after  this  point  it  increases,  the  losses  through 


314 


LOCOMOTIVE  PERFORMANCE. 


wiredrawing  being  greater  than  the  thermodynamic  gain  due  to  the 
increase  of  piston  speed.  Referring  to  the  figures  above,  there  can 
be  no  doubt  but  that  the  change  from  23.7  pounds  to  24.9  pounds  is 
due  to  wiredrawing.  If  for  this  series  of  tests  the  steam  consump- 
tion had  been  obtained  for  a  speed  of  60  miles,  it  would  have  shown 
an  increase  of  two  pounds,  or,  say,  10  per  cent  above  the  minimum. 

In  conclusion,  therefore,  with  reference  to  wiredrawing  with  in- 
crease of  speed,  it  may  be  said  that  its  presence  is  a  necessary  accom- 
paniment of  valves  and  gears  now  common ;  that  is,  it  serves  a  useful 
purpose  in  regulating  the  demands  which  the  cylinders  make  upon 


50 


40 


Cut-Off 


Per  Cent 


of         Stroke 


15 


FIG.  192. 


the  boiler,  but,  at  the  highest  speeds,  it  is  responsible  for  some 
increase  in  steam  consumption. 

157.  Improved  Valve-gears. — Countless  devices  have  been  proposed 
affecting  either  the  valve  or  the  gear  which  gives  it  motion,  whereby 
the  card  may  be  made  larger  than  that  which  results  from  the  normal 
link-driven  valve.  A  typical  improved  card  is  shown  at  A,  Fig.  192. 
Concerning  such  devices  it  should  be  noted  that  it  is  usually  assumed, 
though  the  assumption  is  erroneous,  that  anything  which  increases  the 
area  of  an  indicator-card  is  desirable.  For  example,  in  Fig.  192,  for  20 
per  cent  cut-off  and  a  speed  of  40  miles  an  hour  (card  A) ,  the  plain  out- 
line is  the  normal  card  around  which  has  been  drawn  a  so-called  im- 
proved card.  The  difference  is  the  shaded  area  and  is  presumably  the 
result  of  the  adoption  of  some  new  form  of  gear.  Obviously,  the  shaded 


LOCOMOTIVE  VALVE-GEARS.  315 

area  represents  increase  of  power.  The  first  mistake  that  is  made 
concerning  the  change  is  that  the  increase  in  power  results  in  no 
expense.  Again,  while  the  truth  of  the  preceding  statement  may 
be  admitted,  it  is  often  urged  that  one  may  measure  pressure  and 
volume  represented  by  two  indicator-cards,  such  as  are  shown  by 
Fig.  192,  and  derive  therefrom  an  estimate  of  the  relative  amount  of 
steam  used  per  horse-power  per  hour  under  the  conditions  which  each 
represent.  Such  estimates  are,  in  fact,  fairly  reliable  when  made 
between  cards  agreeing  closely  in  form,  and  when  all  conditions  of 
running  are  the  same,  but  as  a  general  proposition  nothing  is  more 
misleading.  If  there  are  differences  in  speed,  or  in  initial  or  final 
pressure,  or  in  the  number  of  expansions,  the  percentage  of  the  total 
amount  of  steam  used,  which  is  shown  by  the  indicator,  will  change. 
Anything  which  may  produce  a  change  in  the  temperature  of  the 
metal  of  the  cylinder  at  any  one  point  in  its  cycle  is  likely  to  produce 
changes  in  the  whole  cycle.  As  is  well  known,  a  considerable  per- 
centage of  the  steam  drawn  from  the  boiler  for  each  stroke  of  the 
engine  condenses  on  entering  the  cylinder.  While  the  interchange 
of  heat  causes  some  change  in  the  amount  of  water  in  the  cylinder  as 
the  piston  proceeds  on  its  course,  by  far  the  larger  part  of  the  initial 
condensation  continues  in  the  cylinder  until  the  exhaust-port  is  open, 
when  it  flashes  into  steam  and  disappears  with  the  exhaust.  While 
the  process  is  a  complicated  one,  and  cannot  within  the  limits  of  this 
chapter  be  accurately  defined,  the  fact  is  that  any  change  in  the 
form  of  any  line  bounding  an  indicator-card  has  its  effect  upon  the 
amount  of  steam  which  must  be  admitted  to  make  up  the  loss  due  to 
initial  condensation.  A  change  in  the  cycle  remote  from  the  period 
of  admission  may  have  as  pronounced  an  effect  on  the  quantity  of 
steam  required  as  a  change  occurring  during  the  period  of  admission 
itself.  There  is,  in  fact,  no  way  to  measure  the  performance  of  a 
steam-engine  but  by  a  process  which  determines  the  actual  weight 
of  the  feed  or  the  exhaust.  Again,  a  further  illustration  of  the  fact 
that  a  mere  increase  in  the  area  of  an  indicator-card  is  not  significant 
is  to  be  found  in  the  ease  with  which  such  increase  of  area  may  be 
secured.  In  locomotive  practice  it  is  quite  unnecessary  to  adopt  a  new 
gear.  If.  under  the  conditions  prescribed,  the  normal  card  A  at  20 
per  cent  cut-off  (Fig.  192)  is  not  large  enough  for  the  work,  the  reverse- 
lever  may  be  advanced  on  its  quadrant  until  the  cut-off  is  35  per 
cent,  whereupon,  in  this  particular  case,  the  normal  card  B  be- 
comes equal  in  size  with  the  card  representing  an  assumed  im- 


316  LOCOMOTIVE  PERFORMANCE. 

proved  gear.  The  real  questions,  therefore,  may  generally  be  stated 
as  follows:  Is  the  improved  card  at  20  per  cent  a  better  card  than 
the  normal  card  of  equal  area  at  35  per  cent  cut-off?  Will  the  former 
yield  a  horse-power  upon  the  expenditure  of  less  steam  than  the 
latter?  It  is  upon  this  latter  statement  that  the  argument  rests.  No 
device  which  seeks  to  improve  the  steam  distribution  in  a  locomotive 
can  succeed  which  does  not  save  steam  when  compared  with  devices 
previously  in  use.  In  proportion  as  it  saves  steam  it  both  increases  the 
efficiency  of  the  engines  and  increases  their  maximum  power,  for 
since  the  boiler  capacity  is  limited  a  pound  of  steam  saved  is  a  pound 
of  steam  available  for  additional  services. 

Turning  now  to  a  consideration  of  the  margin  upon  which  those 
who  would  improve  valve-gears  have  to  work,  it  must  be  admitted 
that  it  is  not  large.  Results  have  already  been  quoted  which  prove  that 
the  locomotive  with  all  its  wiredrawing  gives  a  horse-power  in  return 
for  less  than  24  pounds  of  steam  per  hour.  This  is  near  the  minimum. 
From  this  performance  of  a  simple  locomotive  having  a  normal  valve- 
gear,  with  its  narrow  port-openings  and  wiredrawing  effects,  we  may 
turn  to  the  Corliss  engine,  the  action  of  which  is  generally  accepted 
by  all  improvers  of  locomotive  valve-gears  as  a  standard  of  perfection. 
Such  an  engine,  with  its  large  port-opening  and  its  prompt  movement 
of  the  valves,  can  in  fact  be  relied  upon  to  give  as  good  a  performance 
as  engines  having  any  other  type  of  valve-gear  operating  under  similar 
conditions  of  speed  and  pressure.  Corliss  engines,  having  cylinders 
which  are  comparable  in  size  with  those  of  locomotives,  and  which 
work  under  a  similar  range  of  pressure,  are,  however,  not  common, 
and  hence  it  is  not  easy  to  command  data  for  the  proposed  compari- 
son. Generally,  simple  Corliss  engines  work  under  a  lower  pressure 
than  locomotives.  A  good  performance  for  a  simple  Corliss  engine 
exhausting  into  the  atmosphere  is  that  of  an  18X48  Harris-Corliss 
engine,  for  which  the  steam  consumption  was  23.9  pounds  per  hour.* 
The  steam  pressure  supplied  this  engine  was  only  96  pounds  by 
gauge.  On  the  basis  given  the  engine  should,  when  supplied  with 
steam  at  180  pounds,  which  is  the  pressure  under  which  the  locomo- 
tive data  were  obtained,  require  less  than  23  pounds  of  steam  per 
horse-power  per  hour.  Straining  the  facts  applying  to  the  two  classes 
of  engines  as  widely  apart  as  a  knowledge  of  existing  data  will  pos- 
sibly permit,  we  may  assume  that  a  Corliss  engine,  if  given  the  advan- 

*  Peabody's  Thermodynamics. 


LOCOMOTIVE   VALVE-GEARS. 


317 


tage  of  the  high  steam  pressure  and  high  piston-speed  common  in 
locomotive  service,  may  give  a  horse-power  hour  on  the  consumption 
of  two  pounds  less  of  steam,  or  approximately  8  per  cent  less  than 
the  locomotive.  This,  then,  is  the  margin  upon  which  those  who 
seek  to  improve  the  locomotive  valve-gear  must  expect  to  work. 
While  it  is  well  worth  attention,  it  cannot  revolutionize  practice. 

158.  Foreign  Valve-gears. — Having   now  considered  the  defects 
and  merits  of  the  link  motion,  we  may  inquire  concerning  other  forms 


Stationary  Link 
FIG.  193. 

of  gears  which,  in  foreign  countries  at  least,  are  in  common  use.  In 
England  one  occasionally  sees  the  stationary  link,  as  shown  by  Fig. 
193,  the  link-hanger  of  which  is  suspended  from  a  fixed  pin,  A,  while 
the  reverse-shaft  is  connected  with  a  radius-rod  which  communicates 
the  motion  of  the  link  to  the  valve-spindle.  A  modification  of  this 
gear  is  -found  in  the  straight  or  Allen  link,  shown  by  Fig.  194,  in 


FIG.  194. 

which  both  the  link  and  the  radius-rod  have  connection  with  the 
reverse-shaft,  which  in  reversing  causes  them  to  move  in  opposite 
directions. 

The  Joy  gear  (Fig.  195),  which  has  been,  and  still  is,  extensively 
used  in  English  practice,  requires  no  eccentric,  but  receives  its  motion 
directly  from  the  main  rod.  The  reversal  of  the  engine  and  changes 


318 


LOCOMOTIVE  PERFORMANCE. 


in  the  travel  of  the  valve  are,  in  this  gear,  accomplished  by  varying 
the  inclination  of  the  curved  guide  along  which  a  block  is  forced  to 
travel  with  each  reciprocation  of  the  main  rod.  The  guide  remains 
stationary,  except  as  acted  upon  by  the  reverse-lever. 


Joy  Gear 
FIG.  195. 

As  a  last  example  from  foreign  practice  is  presented  the  typical 
gear  of  Continental  Europe,  namely,  the  Walschaert  gear  (Fig.  196). 
In  this  gear  motion  is  derived  from  the  cross-head  and  from  a  single 
eccentric,  or,  where  the  gear  is  outside  of  the  frame,  from  a  return- 
crank.  These  motions  are  so  combined,  by  means  of  a  system  of 


FIG.  196. 

connected  rods  and  a  link,  as  to  give  the  usual  motion  to  the  valve. 
A  radius-rod,  connecting  with  the  link-block,  receives  motion  from 
the  reverse-shaft  in  reversing  and  in  changing  the  travel  of  the  valve. 
The  fact  concerning  these  foreign  gears  which  is  to  be  emphasized 
is  that  they  all  give  a  motion  to  the  valve,  which  may  be  repre- 
sented by  a  valve  ellipse,  such  as  that  shown  by  Fig.  191.  There 
are  minor  differences  in  the  character  of  the  resultant  motion 


LOCOMOTIVE  VALVE-GEARS.  319 

which  for  the  present  purpose  need  not  be  discussed,  the  impor- 
tant fact  being  that  the  mechanisms  in  question  are  not  to  be  regarded 
as  reform  gears.  They  are  not  to  be  contrasted  with  the  Stephenson 
link  motion,  but  compared  with  it.  They  do  not  exist  because  they 
give  a  better  steam  distribution  than  is  obtained  from  the  link  motion 
of  this  country,  and,  except  as  may  be  hereinafter  suggested,  they 
are  not  superior  to  the  gears  common  in  this  country.  With  this 
understanding  of  the  matter,  we  may  now  examine  the  several  gears 
referred  to,  and  seek  to  find  a  reason  for  their  existence  in  the  con- 
ditions under  which  they  are  used. 

159.  Adaptability  of  Valve-gears. — From  that  which  has  already 
been  stated,  it  may  be  surmised  that  the  Stephenson  link  motion,  as 
used  upon  American  locomotives,  constitutes  a  convenient  and  accept- 
able gear.  There  are  at  least  four  good  reasons  why  this  is  so,  which 
may  be  enumerated  as  follows : 

1.  The  gear  gives  a  satisfactory  distribution  of  steam. 

2.  Its  design  readily  adapts  itself  to   conditions  involving  the 
use  of  a  rocker  between  the  axle  and  the  valve,  and  the  rocker  has 
until  recently  been  regarded  as  an  essential  element  in  the  design  of 
the  American  locomotive. 

3.  The  accessibility  of  the  forward  driving-axle,  and  the  unoccupied 
space  between  the  frames  in  American  locomotives  as  a  point  of 
attachment  for  eccentric,  has  supplied  ideal  conditions  under  which 
to  develop  the  link  motion. 

4.  Other  forms  of  gear  which  have  been  used  elsewhere  have  been 
thought  impracticable  in  American  service,  because,  owing  to   the 
small  diameter  of  driving-wheels,  which,  until  recently,  have  pre- 
vailed in  this  country,  the  mechanism  of  such  gears  often  extends 
too  near  the  road-bed  for  safety. 

The  stationary  link  (Fig.  193)  has  proven  attractive  to  the  designers 
of  many  English  engines,  because  it  involves  the  use  of  a  single  eccen- 
tric, room  for  which  is  more  easily  found  upon  the  inside  connected 
engines  common  to  English  practice,  where  the  greater  part  of  the 
forward  axle  is  occupied  by  the  cranks,  than  for  the  two  eccentrics 
common  in  American  practice. 

The  Allen  link  responds  to  conditions  similar  to  those  which  are 
met  by  the  stationary  link,  but  is  a  better  design,  since  by  it  the  lines 
of  motion  are  kept  much  nearer  the  lines  of  force. 

The  Joy  valve-gear  is  distinctively  English  in  its  design  and  in  the 
extent  of  its  use  upon  locomotives.  With  the  increased  size  of  the  inside 


320  LOCOMOTIVE  PERFORMANCE. 

connected  locomotive,  the  inside  crank  of  the  forward  axle  gradually  de- 
veloped proportions  which  made  it  difficult  to  find  room  even  for  a  single 
eccentric.  Confronted  with  these  conditions,  the  Joy  gear  naturally 
makes  a  strong  appeal  to  the  designer.  This  gear  takes  its  motion  from 
a  connecting-rod,  and  leaves  the  forward  driving-axle  to  be  occupied 
wholly  by  the  cranks.  For  locomotive  service  the  Joy  gear  is  perhaps 
inferior  to  either  of  the  other  motions  described,  since  irregularities 
in  the  track  materially  affect  the  distribution  of  steam.  For  example, 
when  a  low  joint  permits  the  wheel  to  drop,  the  connecting-rod  par- 
takes of  its  motion  and  carries  it  on  to  the  valve-gear  and  to  the  valve. 

The  Walschaert  gear,  which  is  extensively  used  in  Continental 
Europe,  may  be  either  inside  or  outside  of  the  frames  of  the  engine. 
In  European  practice,  where  inside  cylinders  have  been  much  em- 
ployed, it  has  generally  been  outside  of  the  frames.  Its  design  makes 
a  strong  appeal  to  the  designer  who  is  forced  to  go  outside  of  the 
frame  with  his  valve  motion.  The  gear  is  one  in  which  the  metal  for 
the  parts  may  be  well  distributed  to  transmit  the  stresses  which  are 
brought  upon  them,  and  for  this  reason  it  may  constitute  a  very  stiff 
gear,  though  its  individual  parts  are  relatively  very  light.  For  these 
reasons  its  use  is  likely  to  increase  in  American  practice. 

160.  The  Conclusion  to  be  drawn  from  the  foregoing  discussion 
should  not  be  one  of  discouragement  for  those  who  are  interested  in 
improving  the  locomotive  valve-gear.  Forms  of  gears  now  common 
have  been  commended,  but  this  does  not  imply  that  better  ones  may 
not  be  devised.  The  argument  is,  however,  that  real  and  lasting 
improvement  is  to  be  looked  for  more  along  mechanical  lines  than  in 
attempts  to  improve  the  character  of  the  motion  imparted  to  the 
valve.  While  there  is  a  chance  for  slight  saving  in  fuel,  the  real 
economy  which  may  result  from  the  adoption  of  a  better  gear  is  to  be 
found  in  its  lower  maintenance  cost,  and  in  the  greater  certainty  of 
its  action,  rather  than  in  pounds  of  coal  saved.  What  is  most  desired 
in  a  valve-gear  is  a  mechanism  which,  under  the  adverse  conditions 
of  actual  locomotive  service,  will  give  to  the  valve  that  precision  of 
movement  it  is  designed  to  have.  Along  these  lines  there  is  ample 
opportunity  to  improve  present  practice. 


CHAPTER  XVIII. 

ACTION  OF  THE  COUNTERBALANCE.* 

161.  The  Problem  of  Balancing. — In  the  mechanism  of  a  loco- 
motive the  revolving  parts  at  the  crank-pins,  together  with  the  re- 
ciprocating parts  connected  therewith,  are  balanced  more  or  less 
completely  by  the  addition  of  masses,  or  counterweights,  to  the 
drivers.  But  since  the  counterweights  move  in  circular  paths,  it  is 
only  the  horizontal  component  of  the  radial  force  derived  from  them 
which  can  serve  to  neutralize  the  effect  of  the  reciprocating  parts; 
the  vertical  component  of  all  that  portion  of  the  force  which  applies 
to  reciprocating  parts  is  unbalanced.  This  unbalanced  vertical  com- 
ponent causes  the  pressure  of  the  driver  on  the  rail  to  vary  with  every 
revolution.  Whenever  the  speed  is  high  it  is  of  considerable  magni- 
tude, and  its  change  in  direction  is  so  rapid  that  the  resulting  effect 
upon  the  rail  is  not  inappropriately  called  a  hammer-blow.  Many 
practical  demonstrations  have  been  had  of  the  magnitude  of  the 
forces  involved.  Heavy  rails  have  been  kinked,  and  bridges  have 
been  shaken  to  their  fall,  all  under  the  action  of  heavily  balanced 
drivers  revolving  at  high  speeds. 

Such  results  do  not  ordinarily  follow  from  the  operation  of  the 
locomotive,  and  indeed  cannot  do  so  if  the  locomotive  is  properly 
designed  and  its  speed  is  confined  to  reasonable  limits,  but  the  value 
of  the  vertical  component  of  the  counterbalance  of  a  modern  loco- 
motive is  nevertheless  of  considerable  magnitude.  This  may  be 
judged  from  the  fact  that  the  reciprocating  parts  on  each  side  of  such 
an  engine  exceed  1000  pounds  in  weight,  and  that  the  drive-wheels 
with  which  they  are  connected  not  infrequently  turn  300  revolu- 
tions a  minute. 

*  The  facts  of  this  chapter  were  presented  at  the  New  York  meeting  (Decem- 
ber, 1894)  of  the  American  Society  of  Mechanical  Engineers,  forming  part  of  Vol. 
XVI  of  the  Transactions. 

321 


322  LOCOMOTIVE  PERFORMANCE. 

Various  attempts  have  been  made  to  so  dispose  the  reciprocating 
parts  of  a  locomotive  that,  by  their  inter-action,  a  satisfactory  degree 
of  balance  may  be  secured.  The  de  Glehn  balanced  compound  con- 
stitutes a  well-known  though  not  the  only  example  of  this  type, 
but  such  engines  have  not  yet  come  into  general  use  in  American 
practice,  nor  are  they  likely  soon  to  do  so.  In  dealing  with  the  mech- 
anism now  common  to  American  locomotives  the  most  which  the 
designer  has  been  able  to  accomplish  in  the  matter  of  balancing  is 
in  the  nature  of  a  compromise.  It  is  found  that  the  mass  of  the 
locomotive  is  sufficient  to  absorb  a  portion  of  the  force  set  up  by  the 
motion  of  the  reciprocating  parts,  and  that,  as  a  consequence,  the 
counterweights  put  in  the  wheels  need  not  be  sufficient  entirely  to 
balance  these  parts.  Obviously,  the  less  the  weight  which  is  put  into 
the  wheel  the  smaller  will  be  the  vertical  component  which  constitutes 
the  objectionable  result  arising  therefrom.  An  old  rule  was  to  pro- 
vide balance  in  the  wheel  for  from  75  to  80  per  cent  of  the  weight  of 
the  reciprocating  parts.  A  later  rule  of  the  Master  Mechanics'  Asso- 
ciation provides  that  ^-J-^  part  of  the  weight  of  the  locomotive  may 
be  subtracted  from  the  weight  of  the  reciprocating  parts,  the  difference 
to  be  the  weight  to  be  balanced.  Engines  designed  in  accord  with 
these  rules  are  so  well  balanced  horizontally  that  they  do  not  impart 
vibrations  to  the  trains  they  pull,  while  the  excess  weight  of  the  coun- 
terbalance is  not  sufficient  to  prove  destructive  to  tracks  or  structures. 

The  forces  which  are  brought  into  action  by  the  presence  of  the 
counterbalance  have  been  elaborately  studied,  and  their  precise  effect 
upon  the  pressure  of  contact  between  wheel  and  rail  have  at  times 
been  the  subject  of  much  discussion. 

The  present  chapter  describes  a  series  of  experiments  which  were 
undertaken  at  the  Engineering  Laboratory  of  Purdue  University 
to  demonstrate  the  varying  pressure  between  the  revolving  driver 
and  the  rail  of  the  track.  The  essential  features  of  these  experi- 
ments consisted  in  passing  a  soft  iron  wire  of  small  diameter  under 
the  moving  wheel.  It  was  expected  that  the  varying  thickness  of 
the  wire,  which  had  been  subjected  to  this  process,  would  show  the 
effect  tff  variation  in  pressure  between  the  wheel  and  the  track.  If 
the  wheel  should  leave  the  track  entirely  a  portion  of  the  wire  would 
retain  its  full  diameter;  and  the  real  purpose  of  the  experiments,  as 
originally  planned,  was  to  determine  whether  at  any  speed  easily 
attained  the  driver  would  actually  rise  from  the  track. 

162.  Experimental  Method. — The  apparatus  employed  consisted 
chiefly  of  the  locomotive  Schenectady  mounted  upon  the  Purdue 


ACTION  OF  THE  COUNTERBALANCE.  323 

testing-plant.  To  guide  the  wire,  which  was  to  be  fed  under  the 
driver,  a  length  of  f-inch  gas-pipe  was  secured  to  the  laboratory 
floor  in  front  of  each  driver  included  in  the  experiment  (Fig. 
197).  Three  pipes  were  thus  arranged.  A  deflector  plate  was 
fixed  behind  the  main  driver  to  turn  the  wire  delivered  by  this 
wheel  away  from  the  rear  driver;  but,  except  for  this  plate,  no 
attempt  was  made  to  control  the  course  of  the  wire  after  it  left 
the  wheel.  The  wire  was  of  common  annealed  iron  0.037  inch 
in  diameter.  It  was  prepared  by  being  carefully  straightened  and 
cut  into  lengths  of  twenty  feet;  that  is,  about  3.5  feet  longer 
than  the  circumference  of  the  drivers,  and  two  incheslonger  than 
the  guide-pipe,  in  which  the  lengths  were  to  be  fed  to  the  wheels. 
Wires  thus  prepared  were  laid  in  light  wooden  troughs  to  preserve 
them  from  injury,  and  a  trough  thus  supplied  was  placed  in  line 
with  each  guide-pipe  (Fig.  197).  In  conducting  the  experiments  an 


Guide  JPlpe  .Wire  . ^t—  Boas 


FIG.  197. 

operator  at  each  pipe  drew  a  wire  from  the  trough  and  passed  it 
into  the  pipe,  until  only  about  two  inches  of  the  length  remained  out- 
side. From  the  relative  length  of  guide-tube  and  wire  it  was  known 
that  the  opposite  end  of  the  latter  was  now  close  to  the  driver.  When 
desired  conditions  of  speed  had  been  secured  and  a  signal  given,  a 
touch  of  the  operator's  finger  upon  the  end  of  the  wire  was  sufficient 
to  start  the  opposite  end  under  the  wheel.  The  starting  of  the  wire 
was  accomplished  without  commotion.  The  man  in  charge  was 
conscious  only  of  having  touched  it.  To  an  observer  who  watched 
for  the  wire  as  it  came  from  the  driver  it  gave  the  impression  of  a 
quivering  beam  of  light,  which  an  instant  later  became  a  loosely 
tangled  thread  of  metal.  Or,  if  one  kept  his  eye  upon  the  wall  of  the 
laboratory,  against  which  the  wire  was  allowed  to  impinge,  he  saw 
the  whole  tangled  coil  appear  instantaneously,  and  without  apparent 
cause.  The  initial  end  of  each  wire  was,  in  plan,  of  the  outline  shown 
by  Fig.  198,  from  which  it  would  appear  that  when  the  wire  came 
under  the  influence  of  the  wheel's  motion  the  tensional  stress  upon 
sections  near  the  end,  as  at  A,  exceeded  the  elastic  limit  of  the  material, 
this  stress  being  required  to  impart  motion  to  the  mass  of  wire  to  the 


324 


LOCOMOTIVE  PERFORMANCE. 


right  of  A.  The  weight  of  the  twenty-foot  length  was  about  one 
ounce,  and  the  time  occupied  in  its  passage  was  usually  a  fifth  of  a 
second.  These  facts  will  help  to  show  the  significance  of  the  speeds 
used  in  the  experiments. 


FIG.  198. 

The  speed  of  the  locomotive  was  noted  from  a  registering-counter, 
and  also  by  a  Boyer  speed-recorder,  a  permanent  record  being  obtained 
from  the  latter  instrument.  To  assist  in  connecting  the  effect  pro- 
duced on  the  wire  with  definite  phases  of  the  wheel's  motion  a  nick 
was  made  with  a  sharp  chisel  across  the  face  of  each  driver,  in  line 
with  the  counterweight,  as  at  A  (Fig.  199).  An  impression  of  this 
nick  was  sharply  defined  upon  every  wire  that  passed  under  it.  The 
initial  end  of  the  wire  could,  as  has  been  stated,  be  determined 
by  an  examination;  but  to  leave  no  doubt  as  to  this  matter,  and  for 
the  purpose  of  giving  a  second  reference  point,  one  of  the  wheels  was 
marked  with  two  parallel  lines  ninety  degrees  from  the  first  reference 
line,  as  atC  (Fig.  199). 


Weight  with  tcJiich  each  driver  presses 
on  rail  when  at  rest,  14}OOO  Ibs. 


297  Ibs, 


It  was  found  by  a  comparison  of  reference  marks  that  distances 
along  the  length  of  the  wires  could  be  taken  as  representing  equal 
distances  around  the  face  of  the  wheel.  Thus,  the  length  of  each  wire 
being  greater  than  the  circumference  of  the  wheel,  it  would  some- 
times happen  that  a  single  wire  would  receive  two  impressions  from 
the  same  reference  mark,  the  distance  between  the  two  points  thus 
impressed  upon  the  wire  being  found  equal  to  the  circumference 
of  the  wheel.  This  fact  made  it  easy  to  connect  effects  left  upon  a 
wire  with  the  wheel  positions  (crank-angles)  producing  them. 

Many  of  the  wires  produced  by  the  experiment  described  have 


ACTION  OF   THE  COUNTERBALANCE. 


325 


since  been  carefully  calipered  at  five-inch  intervals;  the  results  plotted, 
and  a  smooth  curve  drawn  through  the  points  thus  located.  Some 
of  the  results  thus  obtained  are  presented  as  Figs.  200,  201,  and  202, 


© 


04    5       10      J5      20      25       30 


•to'%w%%Wi%-  '/w£-  %''::ft 


40      45      50       55      60      65. 


E 


Fortcard  Driver  — —   ItigJit  Side 


75      80      85      W 


Bear  Driver — Bight  Side 
FIG.  200. 


the  points  representing  the  actual  thickness  of  the  wires  being  desig- 
nated by  means  of  small  circles.  It  will  be  seen  that  all  diagrams 
are  plotted  with  reference  to  definite  wheel  positions. 


Scale    Zeno**1  One  division-^9 

e    Thickness       One  division  *. 


gM  Side       Speed  -5.9  miles  perTiour-3: 


yht  Side      Speed  -  G3  miles  per  hour-  337.2  rev.  per  min. 


Bear  Driver-Right  Side     Speed-65  mites  per  hour  -347. 9  rev.  per  min. 


FlG.  201. 

163.  The  Balance  of  the  Locomotive. — Before  attempting  a  dis- 
cussion of  results  in  detail,  it  is  necessary  to  consider  somewhat  briefly 
the  condition  of  balance  of  the  locomotive  experimented  upon.  The 
engine,  as  delivered  by  its  builders,  was  balanced  for  the  road;  but 
to  increase  its  steadiness  in  the  laboratory  weights  were  afterward 


326 


LOCOMOTIVE  PERFORMANCE. 


added  in  equal  amounts  to  the  several  wheels,  until  a  full  horizontal 
balance  had  been  secured.*  The  revolving  and  reciprocating  parts 
which  required  counterbalancing,  exclusive  of  the  crank-pins  and 


Length 


One  division—  K* 
One  division  =.O1* 


Speed  -BS  wiles  per  hour—  310.5  revolutions  per  minute 

i*+\ 

Wlieel       U  i          Position 


Rear  Driver  -  -  Riyht  Side 


Rear  Driver  --   Left  Side 


5  miles  per  hour—  3^7.9  revolutio 


Rear  Driver  -\- Right  Side 


Rear  Driver  Left  Side 

FIG.  202. 

crank-pin  bosses,  which  are  assumed  to  be  parts  of  the  wheels  them- 
selves, were  found  to  weigh  as  follows : 

Piston  and  piston-rod 297 . 0  Ibs. 

Cross-head  with  part  of  indicator  rigging  attached 170.5    " 

Main  rod 344. 5    " 

Side  rod.  .,  278.0    " 


Total  for  one  side 1090. 0  Ibs. 

For  complete  horizontal  balance  it  was  required  that  the  sum  of 
the  weights,  making  up  the  counterbalance  of  the  two  wheels  on  the 
side  of  the  engine  under  consideration,  should  be  equivalent  to  1090.0 
pounds  acting  at  a  radius  of  one  foot.  To  ascertain  the  distribution 

*  On  January  23,  1894,  the  plant  from  which  the  results  herein  described  were 
obtained  was  destroyed  by  fire.  The  new  plant,  now  in  operation,  does  not  require 
the  locomotive  to  be  in  complete  horizontal  balance. 


ACTION  OF   THE  COUNTERBALANCE.  327 

of  balance  between  the  wheels  it  was  necessary  to  examine  them 
separately.  Calculations  based  upon  drawings  of  the  wheel  centers 
gave  the  following  results: 

Main  Wheel.     Rear  Wheel. 
Balance  cast  in  rim  and  between  the  arms,  plus   the  weights 

added  at  the  laboratory,  all  reduced  to  equivalent  weights 

acting  at  a  radius  of  12  inches 744. 1  725. 7 

Weight  of  crank- pin  and  crank-pin  hub  to  be  subtracted 187. 1  179. 1 

Net  weights  available  to  balance  revolving  and  reciprocating 

parts  acting  upon  the  crank-pins 557 . 0  546 . 6 

The  sum  of  the  net  weights  thus  obtained  for  both  wheels  (1103.6 
pounds)  is  13.6  pounds  greater  than  the  sum  of  the  actual  weights 
to  be  balanced.  The  engine  is  known  to  have  been  in  perfect 
horizontal  balance,  the  experimental  methods  adopted  in  securing 
this  condition  serving  to  indicate  when  the  weights  were  changed 
even  to  the  extent  of  a  single  pound.  The  calculated  weight  in  each 

-1   Q     f\ 

wheel  is,  therefore,  assumed  to  be  —^-  =6.8  pounds  heavier  than  the 

2t 

weights  themselves,  and  this  amount  has  been  subtracted  as  a  correc- 
tion from  the  net  weights  given  above,  making  the 

Main  Wheel.     Rear  Wheel 

Corrected  net  weight  of  counterbalance,  available  to  bal- 
ance revolving  and  reciprocating  parts,  acting  upon  the 
crank-pins 550. 2  539 . 8 

The  weights  of  the  parts  involved,  together  with  certain  dimen- 
sions, are  summarized  in  Fig.  199. 

Taking  the  weights  of  side  rod  and  of  main  rod,  as  already  given, 
and  considering  0.6  of  the  weight  of  the  latter  as  a  revolving  part, 

Main  Wheel.     Rear  Wheel. 
The   excess    of   balance   over   that   required    for   revolving 

parts  alone  is 204. 5  400. 8 

which  shows  66  per  cent  of  the  balance  for  reciprocating  parts  to  be 
in  the  rear  wheel. 

Six  different  rules  for  balancing  locomotives  for  the  road,  reported 
as  being  in  common  use,  give  weights  of  counterbalance  for  the  loco- 
motive in  question,  as  follows: 

Main  Driver.     Rear  Driver. 

Rule  A  (for  freight-engines  only) 467  260 

B  (for  all  classes  of  service) 462  322 

"  C  "  "   "   "   "   547  340 

"  D  "  "   "   "   "   570  340 

"  E  "  "   "   "   "   573  366 

"  F  "  "   "   "   "   588  381 

Average  of  five  rules  from  B  to  F  inclusive 548  350 


328  LOCOMOTIVE  PERFORMANCE. 

Compared  with  these  several  standards  the  weights  of  the  coun 
terbalances  in  the  Purdue  engine  stand  as  follows: 

Main  Wheel.  Rear  Wheel. 

By  Rule  A  (for  freight  service  only)     17.8%  too  heavy     107.6%  too  heavy 
"    B  (for  all  classes  of  service)     19.1%    "        "  67.6%    " 


"   D     "    "       "       "       "  3.5%  too  light  56.9%  " 

"   E     "    "       "       "       "  4.0%    "      "  47.5%  "       " 

"   F     "    "       "       "       "  6.4%    "      "  41.6%  "       " 
By  the  average  of  five  rules  from  B  to 

F  inclusive  ...................  0.4%  too  heavy  54.2%  " 

It  is  evident,  therefore,  that  the  weight  of  the  counterbalance  in  the 
rear  wheel,  from  which  most  of  the  results  about  to  be  discussed  were 
obtained,  is  in  excess  of  that  allowed  by  good  practice,  as  expressed 
by  the  rules  already  given.  But  practice  cannot  always  conform  to 
the  law  by  whic'h  it  assumes  to  be  governed.  It  often  happens  where 
wheels  are  of  small  diameter,  and  the  connections  are  heavy,  as  in 
mogul  or  consolidation  engines,  that  there  is  not  sufficient  room  in 
the  main  wheel  to  get  in  a  counterbalance  large  enough  for  the  revolv- 
ing parts  alone;  in  this  case,  therefore,  the  balance  for  reciprocating 
parts  of  this  wheel  must  be  taken  by  the  other  coupled  wheels,  in 
addition  to  that  which,  under  the  rules,  would  be  counted  as  properly 
belonging  to  them.  By  this  process  wheels  having  revolving  parts, 
which  are  relatively  light,  are  employed  to  balance  a  larger  per  cent  of 
all  the  reciprocating  weights.  Again,  almost  any  eight-wheeled 
engine,  balanced  in  an  approved  manner,  will,  if  the  coupling-rod  is 
removed,  have  an  excess  of  balance  in  the  rear  wheel  greater  than 
that  for  the  engine  under  consideration;  and  such  engines  are  not 
infrequently  run  while  disconnected. 

These  considerations  will  serve  to  show  that  while  the  total  weight 
of  the  counterbalances  of  the  Purdue  engine  is,  for  reasons  already 
stated,  heavier  than  would  be  considered  necessary  for  the  road,  and 
while  at  the  time  of  the  experiments  the  weights  were  not  well  dis- 
tributed between  the  wheels,  yet  the  conditions  which  existed  are  not 
at  all  rare.  Doubtless  many  wheels  are  running  which  carry  a  greater 
counterbalance,  when  compared  with  the  revolving  weights  to  be 
balanced,  than  did  the  rear  wheel  of  the  Purdue  locomotive. 

164.  Results.  —  Attention  has  already  been  directed  to  the  fact 
that,  in  the  engine  experimented  upon,  the  excess  of  weight  in  the 
counterbalance  over  that  required  for  the  revolving  parts  alone  was 
much  greater  for  the  rear  driver  than  for  the  main  driver.  As  the 


ACTION  OF   THE  COUNTERBALANCE. 

lifting  effect  is  proportional  to  this  excess  of  weight,  it  follows  that" 
wires  run  under  the  rear  driver  were  likely  to  show  more  variation, 
in  thickness  than  those  under  the  main  driver.  Results  of  experi- 
ments upon  this  point  are  shown  by  Fig.  200,  which  represents  wires 
obtained  at  the  same  instant  from  the  main  driver  and  the  rear  driver 
respectively.  It  will  be  seen  that  the  wire  (7),  from  the  main  driver,, 
shows  but  slight  variation  in  thickness,  notwithstanding  the  high 
speed  (312  revolutions  per  minute),  and  it  may  be  said  that  no  wire 
was  ever  obtained  frqm  this  wheel  which  gave  evidence  that  the 
wheel  had  left  the  track.  From  mathematical  considerations  it  can 
be  shown  that  this  wheel  would  not  be  expected  to  lift  at  speeds  below 
80  miles  per  hour  (428  revolutions  per  minute),  and  such  speeds  are 
not  practicable  with  wheels  of  the  diameter  experimented  upon. 

Passing  now  to  an  inspection  of  wire  77  (Fig.  200),  from  the  rear 
wheel,  which  was  obtained  at  the  same  instant  with  wrire  7,  it  will 
be  seen  that  there  is  a  jump  of  the  wheel  just  after  the  counterbal- 
ance has  passed  its  highest  point,  which,  when  compared  with  the 
corresponding  movement  of  the  main  driver,  is  very  pronounced. 
Wires  from  this  wheel  at  higher  speeds  are  shown  by  Fig.  201.  In 
this  figure  the  full  diameter  of  the  wires  is  in  each  case  shown  by  a 
dotted  line  drawn  parallel  with  the  base  line.  Wire  777,  made  at  59 
miles  (316  revolutions),  shows  that  there  was  an  instant  in  the  passage 
of  the  wire,  corresponding  to  the  point  A,  when  it  was  barely  touched 
by  the  wheel.  Increasing  the  speed  to  63  miles  (337  revolutions) 
increased  the  lifting  action  of  the  wheel  to  the  extent  shown  by  wire 
IV  (Fig.  201).  At  the  point  B  the  wheel  parted  contact  with  this 
wire,  and  did  not  again  touch  it  until  the  point  C  was  reached,  an 
interval  of  about  40  inches,  the  portion  of  the  wire  between  B  and 
C  being  entirely  round  and  apparently  unaffected  by  its  passage  under 
the  wheel.  A -further  increase  of  speed  gave,  as  is  shown  by  wire  Vr 
a  still  greater  length  of  full  wire,  the  distance  from  D  to  E  being  very 
nearly  equivalent  to  a  quarter-revolution  of  the  driver. 

It  will  be  seen  that  all  of  these  wires  (77  to  V,  Figs.  200  and  201) 
substantially  agree  in  showing  the  maximum  lifting  effect  to  occur 
after  the  counterbalance  has  passed  its  highest  point,  an  effect  un- 
doubtedly due  to  the  inertia  of  the  mass  to  be  moved;  also  in  showing 
that  the  rise  of  the  wheel  from  the  track  is  more  gradual  than  its 
descent.  The  latter  condition  follows  as  a  sequence  of  the  first. 

Portions  of  the  wires  not  shown  on  the  diagrams  do  not  vary 
much  in  thickness.  The  metal  is  rolled  so  thin  by  the  normal  pressure 


330  LOCOMOTIVE  PERFORMANCE. 

of  the  wheel  that  further  increments  of  pressure  do  not  greatly  affect 
it.  The  wires,  therefore,  do  not  emphasize  the  destructive  effect  of 
the  variation  of  wheel  pressure  when  the  change  is  insufficient  to  lift 
the  wheel  from  the  track. 

It  now  remains  to  mention  the  effect  of  certain  disturbing  ele- 
ments, which  are  shown  by  the  experiments,  to  modify  the  actual 
movement  of  the  wheel,  other  conditions  remaining  constant.  For 
the  rear  wheel  these  disturbing  elements  are  all  in  the  nature  of 
vibrations.  The  first  to  be  noticed  is  the  rockkig  of  the  engine  upon 
its  springs,  which  motion  tends  to  vary  the  pressure  of  the  wheel 
upon  the  track  independently  of  the  action  of  the  counterbalance. 
At  one  revolution  the  effect  of  the  rocking  may  oppose  the  action  of 
the  counterbalance,  and  at  the  next  revolution  it  may  supplement 
the  action  of  the  counterbalance  in  producing  a  vertical  movement 
of  the  driver.  Again,  the  effect  of  the  rocking  may  at  a  given  instant 
be  nil,  and  the  wheel  may  rise  under  the  action  of  the  counterbalance; 
but  in  another  instant  the  effect  of  the  rocking  appears,  and  the  path  of 
the  wheel  while  in  the  air  is  modified  and  its  time  of  descent  changed. 
Thus,  the  existence  of  this  vibration  makes  it  impossible  to  duplicate 
wires  with  certainty,  even  though  the  speed  is  constant.  Its  effect  is 
well  shown  by  Fig.  202.  Wires  VI  and  VII  were  taken  from  the  rear 
drivers  at  the  same  instant,  one  from  the  right  side,  the  other  from 
the  left;  the  speed,  therefore,  must  have  been  the  same  for  both. 
The  right  driver  lacked  a  good  deal  of  leaving  its  wire,  but  the  left 
driver  was  in  the  air  for  a  tenth  of  a  revolution.  Again,  wires  VIII  and 
IX  were  made  in  the  same  way  at  a  higher  speed;  and  here,  while 
both  drivers  were  off  the  track,  the  results  are  reversed,  the  right 
driver  giving  the  greater  length  of  full  wrire.  It  will  also  be  seen  from 
the  diagrams  that  not  only  is  the  extent  of  the  vertical  movement 
of  the  driver  modified  by  the  rocking  of  the  engine,  but  the  position 
of  the  wheel  when  such  motion  occurs  is  changed.  It  is  evident, 
therefore,  that  this  movement  of  the  engine  upon  its  springs  will  prove 
a  serious  difficulty  whenever  an  attempt  is  made  to  predict  as  to  the 
precise  movement  of  the  center  of  gravity  of  the  driver,  whether  the 
method  of  investigation  be  mathematical  or  experimental. 

There  appears,  also,  to  be  a  vibration  of  parts,  as,  for  example,  of 
the  wheel  as  a  whole,  these  vibrations  being  of  small  amplitude. 
Evidence  of  the  presence  of  such  vibration  is  shown  by  the  location 
of  points  on  the  diagrams  of  wires,  Figs.  200  to  202,  which  points  repre- 
sent the  thickness  of  the  wires  as  found  by  measurement.  Referring 


ACTION  OF   THE  COUNTERBALANCE.  331 

especially  to  wires  7  and  II  (Fig.  200)  it  will  be  seen  that  the  actual 
thickness  of  the  wire  alternately  increases  and  diminishes  with  every 
point.  The  time  involved  in  passing  from  one  high  point  to  another 
(a  distance  of  ten  inches)  was  about  0.01  of  a  second.  This  vibration 
may  be  traced  on  other  diagrams;  its  amplitude  is  from  two  to  four 
thousandths  of  an  inch  only.  Whether  the  process  of  introducing 
the  wire  starts,  or  has  any  connection  with  this  vibration,  the  experi- 
ment does  not  show. 

A  third  class  of  vibrations  is  made  apparent  by  a  duplication 
upon  the  wire  of  the  reference  mark  on  the  wheel.  As  has  been 
stated  a  light  nick  from  a  sharp  chisel  was  made  across  the  face  of 
the  wheel  to  serve  as  a  reference  mark.  This  nick  leaves  a  clear-cut 
projection  upon  the  wire.  But  at  high  speeds  the  single  nick  across 
the  face  of  the  wheel  leaves  two  projections  upon  the  wire,  showing 
that  after  making  one  impression  the  surface  of  the  wheel  must  for 
an  instant  have  actually  cleared  the  wire  and  then  impressed  itself  a 
second  time.  The  distance  between  these  projections  on  the  wires 
varies  somewhat,  but  is  usually  about  an  eighth  of  an*  inch,  which 
represents  a  time  interval  between  the  two  impressions  of  about 
0.008  of  a  second.  The  contact  between  wheel  and  track  is,  therefore, 
not  continuous,  but  is  a  succession  of  exceedingly  rapid  impacts. 
These  vibrations  cannot  affect  the  wheel  as  a  whole;  they  are  doubt- 
less due  to  the  elasticity  of  the  materials,  and  involve  only  the  parts 
immediately  about  the  point  of  contact. 

165.  Conclusions. — The  results  of  the  experiments  appear  to 
justify  the  following  conclusions: 

1.  Wheels  balanced  according  to  usual  rules  (which  require  all 
revolving  parts,  and  from  40  to  80  per  cent  of  all  reciprocating  parts, 
to  be  balanced,  the  counterbalance  for  the  reciprocating  parts  to  be 
distributed  equally  among  the  several  wheels  connected)  are  not  likely 
to  leave  the  track  through  the  action  of  the  counterbalance,  and 
cannot  do  so  unless  the  speed  is  excessive. 

2.  A  wheel  which,  when  at  rest,  presses  upon  the  rail  with  a  force 
of  14,000  pounds,  and  which  carries  a  counterbalance  400  pounds  in 
excess  of  that  required  for  its  revolving  parts  alone,  may  be  expected 
to  leave  the  track  through  the  action  of  the  counterbalance  whenever 
its  speed  exceeds  310  revolutions  per  minute. 

3.  When  a  wheel  is  lifted,  through  the  action  of  its  counterbal- 
ance, its  rise  is  comparatively  slow,  and  its  descent  rapid.     The  maxi- 
mum lift  occurs  after  the  counterbalance  has  passed  its  highest  point. 


332  LOCOMOTIVE  PERFORMANCE. 

4.  The  rocking  of  the  engine  on  its  springs  may  assist  or  oppose 
the  action  of  the  counterbalance  in  lifting  the  wheel.     It  therefore 
constitutes  a  serious  obstacle  in  the  way  of  any  study  of  the  precise 
movement  of  the  wheel. 

5.  The  contact  of  the  moving  wheel  with  the  track  is  not  con- 
tinuous, even  for  those  portions  of  the  revolution  where  the  pressure 
is  greatest,  but  is  a  rapid  succession  of  impacts. 


CHAPTER  XIX. 
MACHINE  FRICTION. 

166.  A  Statement  of  the  Problem. — The  power  which  is  developed 
in  the  cylinders  of  a  locomotive  is  the  sum  of  that  which  is  delivered 
at  the  draw-bar  and  the  losses  which  occur  between  the  cylinders  and 
the  draw-bar.  These  losses,  in  the  case  of  a  locomotive  upon  the 
road,  include  the  frictional  resistance  of  the  machinery,  the  resistance 
of  the  atmosphere,  and  the  rolling  and  journal  friction  of  the  loco- 
motive-truck and  tender.  Upon  a  testing-plant  the  only  loss  which 
occurs  is  that  due  to  the  factor  first  named.  An  interesting  problem, 
therefore,  which  at  once  presented  itself  with  the  advent  of  the  loco- 
motive testing-plant,  was  a  determination  of  the  amount  of  power 
absorbed  by  the  machinery  under  different  conditions  of  running. 
There  had  been  no  opportunity  previous  to  the  establishment  of  the 
Purdue  plant  to  make  such  a  determination  in  connection  with  loco- 
motives, and  even  in  stationary  practice  the  difficulties  attending  the 
measurement  of  high  power  when  delivered  from  a  fly-wheel  has 
operated  to  limit  available  data  to  plants  which  are  comparatively 
small  in  size. 

The  process  which  must  be  followed  to  determine  the  machine 
friction  of  any  locomotive  under  load  is  one  requiring  accurate  obser- 
vations. This  grows  out  of  the  fact  that  the  value  sought  appears 
as  a  difference  between  two  quantities  which  are  relatively  large. 
The  two  quantities  involved  are  cylinder  power  and  draw-bar  power. 
The  value  of  these  may  be  ten  times  as  great  as  their  difference,  and 
hence  an  error  of  one  per  cent  in  a  determination  of  the  indicated 
power,  or  of  the  draw-bar  stress,  may  mean  an  error  of  ten  per  cent 
in  the  value  of  the  difference  which  is  the  factor  sought.  It  was  with 
a  full  appreciation  of  the  significance  of  this  statement  that  the 
experiments  to  determine  the  machine  friction  of  a  locomotive  were 
undertaken. 

333 


334  LOCOMOTIVE  PERFORMANCE. 

167.  Methods. — Every  efficiency  test  of  the  Purdue  locomotive 
is  expected  to  yield  all  data  necessary  to  a  determination  of  machine 
friction.  The  present  discussion,  however,  deals  chiefly  with  tests 
which  involved  a  short  run  designed  to  give  in  a  few  minutes'  time 
such  data  only  as  is  required  to  determine  the  frictional  loss.  Each 
such  test  was  run  under  prescribed  conditions  of  speed,  steam  pressure, 
cut-off,  and  throttle-opening.  The  engine  having  been  warmed  by 
preliminary  running,  was  brought  under  the  conditions  prescribed 
for  the  tests,  after  which,  upon  signal,  all  observations  were  simul- 
taneously taken.  These  observations  were  four  times  repeated  at 
intervals  of  four  minutes,  during  which  time  the  operation  of  the 
engine  was  maintained  as  nearly  constant  as  possible.  Each  test, 
therefore,  yielde  16  indicator-cards  and  such  observed  data  as  are 
given  in  the  exhibit  of  observed  results  on  page  335.  This  exhibit 
is  a  typical  data  sheet  for  such  a  test. 

In  the  conduct  of  this  work  four  indicators  were  used,  one  of  which 
was  closely  connected  to  each  end  of  each  cylinder.  An  absolute 
drum  motion,  connected  by  short  cords,  was  in  regular  use  upon  the 
locomotive.  Great  care  was  employed  throughout  the  tests  in  ques- 
tion in  keeping  the  indicators  in  perfect  order,  in  working  up  the 
cards,  and  in  checking  numerical  calculations  based  thereon.  Because 
of  these  precautions  it  was  felt  that  the  indicated  power  of  the  engine 
was  obtained  with  a  degree  of  refinement  not  often  equalled  in  loco- 
motive work. 

A  correct  measurement  of  the  power  delivered  at  the  draw-bar 
was  found  to  be  a  matter  of  greater  difficulty.  Accuracy  at  this  point 
involved  not  only  the  design  of  a  traction  dynamometer,  but  also  a 
study  of  the  effect  of  the  mounting  mechanism  upon  the  locomotive 
as  a  whole.  So  serious  were  these  difficulties  that  several  years  passed 
before  accuracy  was  obtained  in  measuring  the  actual  tractive  power 
exerted  by  the  locomotive.  A  brief  description  of  the  nature  of  these 
difficulties  will  be  of  interest. 

168.  Difficulties  Encountered  in  Measuring  Draw-bar  Stresses. — 
When  the  experimental  locomotive  was  first  installed  in  1891,  it 
was  provided  with  a  traction  dynamometer  made  up  of  a  very  simple 
system  of  levers,  which  required  a  dash-pot  of  considerable  size  to 
steady  them.  It  was  soon  found  that  the  delicacy  of  this  apparatus 
was  insufficient  to  permit  a  high  degree  of  accuracy  in  the  determina- 
tion of  draw-bar  stresses.  In  consequence  of  this  conviction,  when, 
in  the  rebuilding  of  the  laboratory  after  the  disastrous  fire  of  1894, 


MACHINE  FRICTION. 


335 


RUNNING  CONDITIONS. 

Speed,  miles  per  hour  (approximate) 25 

Steam  pressure  (approximate) 135 

Reverse-lever,  notch  from  center  forward 3 

Cut-off,  per  cent  of  stroke 45 

Throttle Wide  open. 

OBSERVED  RESULTS. 


Gong. 

Time  of 
Gong. 

Revolution  Counter. 

Pressure. 

Dynamom- 
eter. 

Engine 
Position- 

30  Sec- 
onds 
Before. 

30  Sec- 
onds 
After. 

Differ- 
ence. 

Boiler. 

Dry- 
pipe. 

1 
2 
3 
4 

3.20 
3.24 
3.28 
3.32 

2097 
2637 
3154 
3716 

2223 
2760 
3304 
3837 

126 
123 
150 
121 

136 
126 
126 
128 

132 
124 
124 
125 

5840 
5850 
5690 
5860 

+  1.5 
-fl.5 
+  1.5 
+  1.5 

Totals  

520 

516 

505 

23240 
5810 

+  6 
+  1.5 

Averag* 

33    . 

130 

129 

126 

DERIVED  RESULTS. 

Mean  effective  pressure  (each  value  the  average  of  four  cards). 

Right  head  end 57.03 

' '      crank  end 57 . 11 

Left  head  end 61 . 69 

' '    crank  end 61 . 33 

Indicated  horse-power. 

Right  head  end. 102.28 

' '      crank  end. 99.25 

Left  head  end 110.70 

* '    crank  end 106. 18 

Total 418.41 

Friction,  horse-power. 

Total  I.H.P. 418.41 

Dynamometer    horse-power=  dynamometer    pullxR.P-M. 

X. 0004956.  ...  .  374.32* 


Frictional  horse-power 44. 09* 

Frictional  resistance. 

Mean  effective  pressure  equivalent  to  friction=F.H.P.  -r- 

(.0542XR.P.M.) 6.25* 

Draw-bar  pull  equivalent  to  friction=M.E.P.Xl09.419.  .  .   683.8* 


*  No  correction  applied  for  engine  position. 


336 


LOCOMOTIVE  PERFORMANCE. 


the  opportunity  came  to  improve  the  plant,  it  was  determined  to 
supply  a  dynamometer  of  high  quality.  An  order  was  subsequently 
given  to  the  William  Sellers  Company  for  an  Emery  machine,  con- 
sisting of  a  hydraulic  support,  suitably  mounted  to  receive  the  draw- 
bar, and  a  separate  scale-case,  all  of  which  was  duly  received,  and  has 
since  been  used.  This  machine,  while  capable  of  measuring  stresses 
as  high  as  30,000  pounds,  is  so  sensitive  that  the  pressure  of  one's 
finger  upon  the  front  bolster  of  the  locomotive  will  produce  sufficient 
motion  in  the  whole  mass  of  the  locomotive  to  give  an  indication  upon 
the  dynamometer  scale.  Having  possession  of  so  delicate  an  instru- 
ment, it  was  with  high  expectation  that  tests  to  determine  the  engine 
friction  were  entered  upon  early  in  October  of  the  first  year  of  the 
reestablished  plant. 

After  carrying  out  a  rather  elaborate  series  of  tests  upon  the  plan 
already  outlined,  it  was  found  that  the  results  were  unsatisfactory 
in  that  they  appeared  to  follow  no  law,  and  because  many  of  the 
values  obtained  indicated  negative  friction,  the  draw-bar  power  being 
greater  than  that  of  the  cylinders.  In  entering  upon  the  work  at 
the  beginning  of  a  new  school  year  in  the  fall  of  1895,  it  was  decided 
that  the  failure  of  the  previous  October  had  been  due  to  the  faulty 
position  of  the  locomotive  drivers  upon  their  supporting  wheels,  and 
hence  the  true  position  of  the  drivers  upon  the  supporting  wheels, 
both  when  the  engine  was  at  rest  and  in  motion,  was  first  determined. 

The  importance  of  this  will  be  seen  from  the  following  considera- 
tions :  With  the  locomotive  at  rest,  and  so  located  that  a  line  joining 
the  center  of  each  driver  with  the  center  of  its  supporting  wheel  is 
vertical  (Fig.  203),  no  force  need  be  exerted  along  the  line  of  the 


00 


Line  of  Draw-ba» 


FIG.  203. 


draw-bar  to  hold  the  engine  in  its  position  upon  its  supporting  wheels. 
Moreover,  with  the  engine  in  this  position  and  in  motion  the  indica- 
tion of  the  draw-bar  dynamometer  should  serve  as  a  correct  measure 
of  the  force  transmitted  from  the  drivers  to  the  supporting  wheels, 


MACHINE  FRICTION. 


337 


that  is,  of  the  tractive  force  exerted  by  the  locomotive.  In  the  event, 
however,  that  the  drivers  are  ahead  of  their  neutral  position  on  the 
supporting  wheels,  or  back  of  the  same  (Fig.  204),  it  is  evident  that 
when  the  engine  is  at  rest  force  must  be  exerted  along  the  line  of  the 
draw-bar  to  hold  it  in  position,  and  that  with  the  engine  in  motion 
in  either  of  these  positions  the  indication  of  the  draw-bar  dynamometer 
will  not  measure  the  force  transmitted  from  the  drivers  to  the  sup- 
porting wheels,  unless  corrected  for  the  initial  condition  of  stress  in 
the  draw-bar.  It  is  obvious,  therefore,  that  if  comparisons  are  to  be 
made  between  the  power  developed  in  the  cylinders  and  that  delivered 


FIG.  204. 

at  the  draw-bar  the  position  of  the  drivers  upon  the  supporting  wheels 
must  be  neutral,  or  their  position  must  be  SD  accurately  known  that 
correction  may  be  applied. 

The  significance  of  all  this  was  appreciated  from  the  first,  though 
the  difficulties  in  the  problem  were  not  anticipated.  When  the  loco- 
motive had  been  installed  upon  the  plant  it  had  been  carefully  ad- 
justed to  its  position  while  cold.  The  failure  to  get  consistent  records 
at  the  draw-bar  suggested  that  the  spacing  of  the  driving-axles  might 
change  sufficiently  with  the  increased  temperature  of  the  frame 
resulting  from  working  conditions  to  account  for  the  difficulties 
encountered.  Consequently,  when  the  work  was  next  undertaken 
(September,  1895),  the  wheels  were  lined  up  when  the  engine  and 
boiler  of  the  locomotive  were  heated  to  working  temperature.  More- 
over the  effect  of  machine  stresses  was  also  taken  into  account,  all 
measurements  being  repeated  with  steam  in  the  cylinders,  first  with 


338  LOCOMOTIVE  PERFORMANCE. 

the  reverse-lever  in  forward  motion,  and  afterward  with  the  reverse- 
lever  in  backward  motion,  the  supporting  wheels  being  prevented  from 
turning  by  means  of  the  friction-brakes.  This  process  was  repeated 
for  various  positions  of  the  crank.  The  completion  of  this  programme 
of  preliminary  work  failed  to  disclose  any  gross  errors  in  the  position 
which  the  engine  had  occupied  in  the  previous  tests,  and  trial  runs  to 
determine  values  for  engine  friction  proved  no  more  satisfactory  than 
those  which  had  resulted  from  previous  attempts.  Meanwhile,  the 
locomotive  was  being  occupied  with  work  not  depending  upon  accurate 
records  of  draw-bar  stress. 

Up  to  this  time  the  traction  dynamometer,  an  expensive  machine 
selected  especially  because  of  the  reputation  of  its  type  for  accuracy, 
had  been  accepted  as  a  standard  of  measure  No  one  had  doubted 
its  accuracy.  But  the  experiences  already  recounted,  in  combination 
with  other  events  at  the  laboratory,  required  that  some  effort  be  made 
to  check  its  indications.  This  was  finally  done  by  moving  an  Olsen 
testing-machine  to  the  locomotive  laboratory,  by  disconnecting  the 
dynamometer  from  the  locomotive,  and  by  mounting  the  hydraulic 
head  of  the  dynamometer,  with  all  attached  parts,  upon  the  testing- 
machine  in  such  a  manner  that  a  load  could  be  imposed  upon  it  in 
the  testing-machine  through  the  same  spindle  which  had  previously 
connected  with  the  locomotive  draw-bar.  By  these  means  it  was 
possible  to  apply  to  the  dynamometer  any  desired  load  as  measured 
by  the  beam  of  the  testing-machine,  and  to  determine  the  indication 
which  the  dynamometer  scale  gave  in  response  to  these  loads.  The 
degree  of  accuracy  attending  the  work,  of  course,  was  limited  to  the 
accuracy  of  the  Olsen  machine,  but  this  proved  quite  sufficient  for 
the  purpose.  The  results  of  comparison  proved  that  the  indications 
of  the  dynamometer  were  too  high  and  singularly  irregular. 

These  results  having  been  confirmed  by  a  representative  of  the 
manufacturer,  the  whole  machine  was  shipped  to  the  factory  for  cor- 
rection. It  was  there  recalibrated,  and  in  February,  1896,  was  restored 
to  its  place  in  the  laboratory.  Soon  after  attempts  were  again  made 
to  secure  a  measurement  of  the  machine  friction  of  the  locomotive, 
but  the  results,  while  never  showing  negative  friction  and  while  much 
more  consistent  than  those  previously  obtained,  were  still  too  discor- 
dant to  be  entirely  satisfactory,  whereupon  nothing  remained  but  to 
again  give  attention  to  the  location  of  the  wheels  of  the  locomotive. 
That  this  might  be  more  carefully  investigated  than  on  previous 
occasions  a  telltale  was  arranged  to  connect  between  the  locomotive 


MACHINE  FRICTION. 


339 


frame  at  a  point  midway  between  the  two  drivers  and  the  wall  of 
the  laboratory  (Fig.  205).  It  consisted  of  a  small  pointer,  suitably 
mounted,  and  so  proportioned  as  to  magnify  the  actual  movement  of 
the  locomotive  approximately  ten  times.  The  end  of  the  pointer 
passed  over  a  stationary  scale  graduated  from  an  arbitrary  zero 
by  divisions  of  equal  value,  each  of  which  represented  an  actual  move- 
ment of  the  engine- frame  of  an  .0543  of  inch.  The  value  of  this  arrange- 
ment was  to  be  found  in  the  fact  that  any  position  of  the  pointer  indi- 
cated at  all  times  a  certain  relative  position  of  drivers  and  supporting 
wheels.  By  its  aid  the  problem  of  locating  the  drivers  upon  the 
supporting  wheels  resolved  itself  into  the  finding  of  a  "position  cor- 
rection" corresponding  to  the  different  positions  of  this  pointer. 


y     F—    A 

0         <§>         @ 

,11          >  « 

7"                 - 

Point  in  Locomotive                    Secured  to 
Frame  Midway                              laboratory  "Wall 
between  Drivers 

0                       © 

FIG.  205. 

As  it  was  found  that  correct  values  for  draw-bar  stress  could  not 
be  read  directly  from  the  dynamometer,  an  attempt  was  made  to 
determine  the  amount  of  the  position  correction  by  direct  weighings. 
The  method  of  procedure  was  to  move  the  locomotive  by  means  of  .a 
jack-screw,  until  the  pointer  stood  at  zero,  and  with  an  initial  load 
on  the  dynamometer  to  balance  the  scale-beam.  Next,  without 
changing  the  initial  load,  the  locomotive  was  moved  by  means  of  .the 
jack  until  the  pointer  stood  at  each  of  the  several  different  division 
marks  on  the  forward  scale,  and  thence  back  to  zero,  the  dynamometer 
being  balanced  and  readings  taken  for  each  position  both  forward  and 
back.  It  was  expected  that  when  the  dynamometer  readings  thus 
obtained  were  plotted,  they  would  give  a  line  which  would  determine 
the  correction  to  be  applied  to  the  dynamometer  rea-dings  when  the 
engine  was  working  in  any  of  the  given  divisions  experimented  upon. 
The  results,  however,  did  not  justify  the  pains,  since  the  values  ob- 
tained showed  great  irregularities,  and,  while  the  experiment  was 
conducted  with  great  care,  was  carried  out  with  many  variations, 


340  LOCOMOTIVE  PERFORMANCE. 

and  was  many  times  repeated,  it  did  not  suffice  to  give  a  satisfactory 
position  correction.  he  conclusion  reached  was  to  the  effect  that 
minor  forces  were  brought  into  play  whenever  the  engine  was  moved, 
and  that  the  presence  of  these  prevented  the  machine  from  behaving 
in  the  same  way  in  every  different  position.  It  was  thought,  how- 
ever, that  these  would  disappear  if  similar  tests  could  be  made  when 
the  engine  was  in  motion.  To  accomplish  this  involved  the  following 
program  : 

With  the  locomotive  in  any  given  position  and  running  ahead,  the 
pull  registered  by  the  dynamometer  will  be 

DF=MF-F+x,     .......     (18) 

where  Mp  =pull  corresponding  to  the  M.E.P.  in  the  cylinders,  engine 

running  ahead; 

F  =  pull  equivalent  to  the  machine  friction; 
x  =  pull   due   to  engine   position,  which   is  the    correction 
sought. 

With  the  locomotive  in  the  same  position,  running  aback  under 
the  same  conditions  of  speed,  cut-off,  and  steam  pressure  as  when 
running  ahead,  it  may  be  assumed  that  the  machine  friction  will  be 
the  same,  and  consequently  that  the  draw-bar  pull  will  be 

DB=MB-F-X,     .......     (19) 

where  MB  =pull  corresponding  to  the  M.E.P.  in  the  cylinders,  engine 

running  back; 
F  and  x  have  the  same  values  as  above. 

Solving  these  two  equations  for  x,  we  have 


It  will  be  seen  that  equation  20  makes  the  value  of  x,  which  is  the 
correction  for  position,  depend  upon  M  and  D.  Numerical  values  for 
the  former  are  obtained  directly  from  the  indicator-cards,  and  for  the 
latter  by  direct  observation  from  the  traction  dynamometer.  The 
only  assumption  involved  by  the  equation  is  that  the  friction  of  the 
engine  is  the  same,  when  the  same  conditions  of  speed,  cut-off,  and 
initial  pressure  in  the  cylinders  are  maintained,  whether  the  engine  is 
running  ahead  or  aback.  The  value  of  x,  if  considered  positive  when 


MACHINE  FRICTION.  341 

the  engine  is  running  ahead,  must  be  considered  negative  when  the 
e  gine  is  running  aback. 

In  the  application  of  this  program  a  series  of  position  tests  were 
made  in  March,  1898,  with  results  which  were  too  much  at  variance 
one  with  another  to  be  accepted  as  satisfactory.  A  month  later  it  was 
determined  to  repeat  the  work  with  all  of  the  friction-brakes  removed 
from  the  axles  of  the  supporting  wheels,  so  that  the  power  developed 
should  approach  closely  the  friction-load,  whereupon  it  was  found 
that  with  the  engine  running  ahead  there  was  compression  in  the 
draw-bar.  An  investigation  of  the  cause  of  this  unexpected  result 
revealed  the  fact  that  the  friction  of  the  front  trucks  on  the  rails  was 
too  great  to  allow  a  free  movement  of  the  locomotive  forward  and 
back.  Previous  to  this  time  but  little  attention  had  been  given  to  the 
trucks,  the  belief  being  that  the  vibration  of  the  engine  in  motion 
would  be  sufficient  to  overcome  any  resistance  which  they  might  offer. 

A  careful  investigation  at  this  time,  however,  revealed  the  fact 
that  the  rails  which  were  mounted  on  wood  had  yielded  under  the 
pressure  and  vibration  of  the  truck,  becoming  slightly  deformed 
under  each  wheel.  This  fact  having  been  determined,  the  truck  was 
removed,  the  truck  wheels,  which  had  been  cast  in  a  contracting  chill, 
were  ground  truly  round,  the  wooden  support  for  the  rails  was  removed, 
and  the  work  rebuilt  in  masonry  and  capped  with  metal.  The  rails 
were  planed  on  their  upper  surface  and  drawfiled.  The  effect  of 
these  improvements  was  marked,  and  the  results  obtained  from  posi- 
tion tests  which  followed,  when  compared  by  means  of  equation  20, 
gave  evidence  for  the  first  time  of  a  definite  law. 

So  much  improvement  had,  in  fact,  been  effected  by  bettering  the 
mounting  of  the  truck,  that  it  was  finally  decided  to  entirely  elim- 
inate friction  from  this  source  by  its  entire  removal.  That  this  might 
be  accomplished,  the  front  of  the  engine  was  suspended  from  the  roof 
of  the  laboratory,  the  construction  of  the  building  being  such  as 
readily  to  admit  of  such  a  plan  (Fig.  206).  Two  rods,  17  feet  in 
length,  connected  the  front  bolster  with  their  point  of  support.  With 
the  engine  at  zero  position  upon  the  supporting  wheels,  these  rods 
were  made  to  stand  vertically.  Thus  supported,  the  front  of  the 
engine  was  as  free  to  move  in  any  direction  as  a  pendulum  of  equal 
weight. 

With  the  engine  thus  suspended,  tests  were  run  to  determine  the 
indicated  power-  and  the  tractive  power  for  each  position  of  the  indi- 
cator (Fig.  205).  By  the  manipulation  of  the  turn-buckle  connecting 


342 


LOCOMOTIVE  PERFORMANCE. 


between  the  draw-bar  and  dynamometer,  the  pointer  of  the  telltale 
was  allowed  to  occupy  in  succession  the  several  positions  along  its 
scale,  and  in  each  position  observations  were  made  in  triplicate.  This 
was  done  with  the  engine  running  both  ahead  and  aback.  The  reverse- 
lever  was  in  all  cases  in  its  extreme  position.  The  speed  was  as  nearly 
as  possible  the  same  for  each  test,  and  the  load  was  only  that  due 


Roof  Beam 


FIG.  206. — Method  Used  to  Determine  Position  of  Engine. 

to  the  friction  of  the  supporting-wheel  axles.  A  summarized  state- 
ment of  the  results  of  these  tests  appears  as  Table  LXVIIL,  and  the 
value  of  the  position  correction,  as  obtained  by  plotting  these  values, 
is  shown  by  Fig.  207.  The  straight  line  of  this  diagram  represents 
the  average  value  of  the  readings  given  in  Table  LXVIIL  The  equa- 
tion for  this  line  is 

a  =  -199  4- 44  y, (21) 

where  x  =  pull  due  to  engine  position  (  +  if  tension,— if  compression); 
y  =  position  of  locomotive  as  shown  by  pointer  (+  if  forward, 
—  if  back  of  the  arbitrary  zero). 


MACHINE  FRICTION. 


343 


The  point  at  which  the  mounting  mechanism  has  no  effect  on  the 
draw-bar  is  given  as  +4.52. 


250 

£ 

\ 

200 

a 

'7  a 

150 

n 

B+ 

100 

0 

§ 

r 

2 

^ 

CH 

x 

* 

c 

) 

y 

Pos 

tun 

4 
of  Engi 

3 
ne  as  SI 

own  by 

Poi 

Itl'l 

Positior 

of' 

Kny 

3 

ne  as  SI 

4  S\ 

lovvixoy 

5 
Pointer 

. 

-1 

ack 

froi 

nC 

?nt« 

t 

+  : 

"or\ 

/ard  fro 

11  C 

>ute 

J/C 

3 

a 

/ 

100 

( 

x 

/ 

) 

150 

| 

x 

S 

3 

/ 

( 

Xc 

>|'S 

/ 

250 

^ 

x 

»§' 
II 

^ 

^ 

300 

0 

/ 

'  C 

) 

B 

^ 

350 

a 

j 

y 

/ 

400 

/ 

> 

/ 

FIG.  207. — Draw-bar  Pull  Due  to  Engine  Position. 

When  the  locomotive  is  in  the  position  corresponding  with  the 
zero  position  of  the  pointer,  which,  it  will  be  remembered,  was  arbit- 
rarily located,  y  will  equal  zero  and 


X--199. 


344 


LOCOMOTIVE  PERFORMANCE. 


TABLE  LXVIII. 

INDICATED  AND  TRACTIVE  POWER  FOR  DIFFERENT    POSITIONS   OF 
THE  DRIVERS   ON  SUPPORTING  WHEELS. 


Engine  Running  Ahead. 

Engine  Running  Aback. 

.o'-s'e-i 

41 

1 

ons  per 

2* 

|S 

i; 

ffjj 

OJ 

1 

ons  per 

5J 

J§ 

1 

p  to" 

si  H 

|§|| 

ine  Posit 
aic  Sum 
dVII)  +  : 
1.  Compre 

£j 

33 

3 

fij 

£.2 

§J 

"3 

fj 

£j§ 

lfr^       *3   ^  •   ttC  ^   C  *O 

^£  a  J«g  i| 

ffe 

R 

1 

£  J 

o  -^ 

S-SjS 

6s' 

PI! 

§»H 

£  « 

i 

3  „; 

m 

gjf 

laiilel^l 

j-sj|  -2<«  '• 

§i 

31 

KS 

-  3 

Jftj^. 

If 

JH*  Q 

al 

tf.2 

.  3 

l^-rf 

S  « 

•a  g 

Q£^GoQG_;35 

i1 

IF 

tb 
§ 

3§l 

il 

lS-§£ 

11 

H 

laii 

•1 

"gJS"O  J3 

isSs 

02 

02 

PH 

PH 

£ 

02 

* 

PH 

PH 

PH 

£ 

i. 

II. 

III. 

IV. 

V. 

VI. 

VII. 

VIII. 

IX. 

X. 

XI. 

XII. 

0 

29 

54 

2552 

2245 

307 

25 

53 

2151 

2203 

-52 

-179 

+  2 

27 

55 

2405 

2168 

237 

25 

52 

2146 

2154 

-8 

-123 

+  4 

25 

61 

2155 

2016 

139 

26 

51 

2225 

2162 

63 

-  38 

+8 

29 

48 

2544 

2532 

12 

27 

49 

2315 

2149 

166 

+  77 

+  4 

27 

53 

2300 

2210 

90 

27 

48 

2264 

2168 

96 

+     3 

+  2 

28 

51 

2397 

2209 

188 

24 

58 

1925 

1913 

12 

-  88 

0 

27 

50 

2368 

2097 

271 

22 

59 

1848 

1932 

-84 

-178 

-2 

26 

52 

2276 

1903 

373 

25 

52 

2129 

2345 

-216 

-295 

-4 

24 

56 

2097 

1657 

440 

25 

52 

2183 

2490 

-307 

-374 

-6 

23 

53 

2071 

1595 

476 

25 

51 

2193 

2516 

-323 

-400 

-4 

23 

56 

2042 

1565 

423 

26 

50 

2249 

2560 

-311 

-367 

-2 

23 

57 

1968 

1582 

386 

25 

49 

2212 

2456 

-244 

-315 

0 

23 

56 

2051 

1765 

286 

23 

49 

2295 

2448 

-153 

-220 

That  is,  under  these  conditions,  199  pounds  must  be  subtracted  from 
the  observed  reading  of  the  dynamometer;  corrections  for  other 
positions  may,  of  course,  be  read  directly  from  the  diagram  (Fig.  207), 
or  found  by  means  of  equation  21. 

It  will  be  evident,  also,  that  having  the  data  which  appears  in 
Table  LXVIII.,  the  value  of  the  correction  for  any  position  of  the  loco- 
motive may  easily  be  calculated  by  means  of  equation  20.  The  values 
given  are:  In  Col.  IV,  MF]  in  Col.  V,  Dp]  in  Col.  IX,  MB',  and  in  Col. 
X,  DB  of  this  equation.  The  application  of  this  equation  to  the  data 
of  any  given  position  will  give  a  result  consistent  with  that  which 
appears  in  the  same  line  under  Col.  XII. 

With  reference  to  the  accuracy  of  the  foregoing  conclusions,  it 
should  be  noted  that  data  was  obtained  for  all  positions  of  the  loco- 
motive from  1.5  to  —.25,  a  range  which  extends  far  beyond  the  limits 
of  Table  LXVIII.  and  Fig.  207.  The  extreme  values,  while  of  use  in 


MACHINE  FRICTION.  345- 

determining  the  slope  of  the  plotted  line,  are  omitted  as  unnecessary 
to  the  present  discussion. 

Finally,  with  reference  to  the  long  and  laborious  process  which  has; 
been  described,  the  fact  should  be  emphasized  that  most  of  the  diffi- 
culties encountered  were  of  a  kind  which,  in  the  light  of  past  experi- 
ence, should  have  been  easily  avoided.  It  would  be  wholly  wrong  to 
conclude  that  a  locomotive  testing  plant,  constructed  along  the  lines 
developed  at  Purdue,  is  defective  as  an  instrument  for  measuring 
the  tractive  power  of  a  locomotive,  or  that  accuracy  of  observed  data 
is  obtained  at  the  expense  of  unusual  effort.  It  should  be  clear  that 
defects  in  the  rating  of  the  dynamometer,  which  for  so  long  a  time 
proved  so  perplexing,  should  not  be  charged  against  the  principle 
underlying  the  plant.  The  importance  of  one  rule  of  practice,  however r 
is  emphasized  by  the  experience  in  question.  It  is  to  the  effect  that, 
for  very  accurate  work,  too  much  reliance  should  not  be  placed  upon 
vibration  as  a  means  of  overcoming  truck  friction.  The  rail  surface 
should  be  in  perfect  form.  If  the  same  locomotive  is  to  be  operated 
on  a  plant  for  a  considerable  time,  it  will  be  necessary  frequently  to 
inspect  the  rails,  to  make  sure  that  corrosion  or  side  movement  of 
wheels  has  not  formed  incipient  grooves  under  the  tread  of  each 
wheel.  If  care  is  given  this  matter,  and  if  the  drivers  are  made  plumb 
over  the  supporting  wheels  by  careful  measurement,  the  record  of 
the  dynamometer  will  be  sufficiently  accurate  for  every  practical 
purpose,  even  though  the  stresses  to  be  measured  are  relatively  light, 

169.  Friction  Tests  and  their  Results. — Having  obtained  a  dyna- 
mometer which  could  be  depended  upon,  and  having  determined  the 
engine  position  with  such  care  as  to  permit  the  measurement  of  draw- 
bar stresses  with  a  high  degree  of  accuracy,  a  series  of  tests  to  deter- 
mine  machine  friction  were  undertaken.  In  proceeding  with  the- 
work,  the  locomotive  having  been  warmed  by  preliminary  running, 
was  brought  under  conditions  for  which  information  was  desired r 
Upon  signal,  indicator-cards  were  taken,  the  draw-bar  pull  ascer- 
tained, and  all  running  conditions  observed.  All  observations  were 
taken  simultaneously,  and  were  three  times  repeated  at  intervals  of 
four  minutes,  after  which  other  conditions  of  running  were  sought 
and  another  test  was  entered  upon.  Tables  LXIX.  and  LXX.  which 
in  effect  constitute  a  single  table,  give  in  each  line  the  average  of  the 
three  observations  making  up  one  test  and  the  calculated  values 
obtained  therefrom.  The  running  conditions  are  set  forth  by  Cols. 
2  to  7  the  power  developed  in  the  cylinders  and  at  the  draw-bar  by 


346 


LOCOMOTIVE  PERFORMANCE. 


.  TABLE  LXIX. 
RESULTS  OF  FRICTION  TESTS. 


J 

a 

9 
* 

1 

1 

2 
3 
4 

6 
6 

7 
8 

9 
10 
11 
12 
13 

14 
15 

16 
17 

18 
19 
20 
21 

22 
23 
24 
25 
26 
27 
28 
29 
1 

Speed. 

Cut-off.    * 

Pressure 

M.E.P. 

Miles 
per 
Hour. 

2 

R.P.M. 

Notch 
For- 
ward 
from 
Center. 

Per 

Cent 
of 
Stroke. 

Boiler. 

Dry- 
pipe. 

Right. 

Left. 

Aver- 
age. 

H.E. 

C.E. 
9 

H.E. 

10 

C.E. 

3 

4 

5 

6 

7 

8 

11 

12 

47.35 
42.36 
38.83 
37.30 
34.43 
31.00 
27.29 
23.33 

14.35 
15.04 
25.16 
25.70 
35.64 
35.47 
46.68 
56.83 

14.29 
24.94 
35.96 

46.48 
58.06 

77.22 
80.94 
135.4 
138.3 
191.8 
190.9 
251.2 
305.8 

76.89 
134.2 
193.5 
250.6 
312.4 

25 
25 
25 
25 
25 
25 
25 
25 

132 
128 
129 
130 
132 
128 
132 
131 

128 
124 
124 
127 
126 
125 
129 
127 

42.87 
37.30 
34.05 
33.51 
30.64 
25.98 
23.17 
18.42 

51.77 
44.98 
42.67 
40.71 
36.86 
33.33 
28.30 
24.34 

46.95 
42.17 
38.98 
35.75 
.34.33 
30.71 
27.69 
24.49 

47.82 
44.98 
39.64 
39.24 
35.91 
34.30 
30.00 
26.09 

2 
2 
2 
2 
2 

35 
35 
35 
35 
35 

45 
45 

129 
124 
126 
125 
123 

131 
125 

135 
132 

125 
119 
121 
121 
122 

128 
118 

57.16 
46.84 
38.79 
32.04 
25.04 

63.74 
53.03 
45.23 
37.61 
29.75 

61.49 
51.62 
44.66 
37.57 
30.64 

61.85 
52.  7i 
46.78 
38.83 
31.74 

61.06 
51.07 
43.86 
26.51 
29.29 

66.73 
54.28 

25.48 
36.70 

137.1 
197.5 

3 
3 

9 
9 

2 
2 
2 
2 

61.78 
49.85 

66.82 
54.68 

69.65 
56.10 

68.68 
56.50 

14.38 
14.74 

77.40 
79.30 

191.6 
191.9 
193.1 
191.5 

80 
80 

81 
73 

65.74 
60.06 

68.26 
62.49 

70.44 
62.17 

72.13 
63.35 

69.14 
62.02 

35.61 
35.66 

35.88 
35.59 

35 
35 
35 
35 

148 
126 
95 

76 

104 
100 
95 
76 

31.23 
30.66 

27.77 
21.35 

32.86 
33.00 
32.77 
33.61 
34.69 
34.47 
35.27 
30.78 

37.26 
35.75 
31.80 
24.99 

44.16 
45.80 
44.57 
45.45 
43.79 
41.22 
41.57 
39.34 

37.05 
35.35 
31.56 
22.91 

40.00 
41.30 
40.05 
41.02 
41.24 
39.73 
41.14 
36.37 

38.48 
35.93 
33.61 
25.10 

36.00 
34.42 
31.18 
23.59 

39.67 
40.83 
40.15 
40.87 
40.34 
38.80 
39.83 
35.77 

24.16 
25.09 
25.18 
25.46 
25.27 
25.18 
25.46 
26.48 

130.0 
135.0 
135.5 
137.0 
136.0 
135.5 
137.0 
142.5 

1 
1 
1 
1 
1 
1 
1 
1 

25 
25 
25 
25 
25 
25 
25 
25 

127 
129 
124 
126 
131 
129 
132 
130 

124 
125 
122 
123 
129 
127 
130 
124 

41.64 
43.24 
43.23 
43.40 
41.46 
39.78 
41.35 
36.  5f 

Cols.  9  to  18,  and  the  friction  loss  as  expressed  in  various  terms  by 
Cols.  19  to  22  The  dynamometer  pull  equivalent  to  the  indicated 
horse-power  (Col.  18),  depends  upon  the  relation  of  cylinder  dimensions 
to  diameter  of  drivers.  It  assumes  no  loss  of  power  in  transmission 
from  the  cylinder  to  draw-bar  and  is  expressed  by  the  equation 

Ibs.  M.E.P.  in  each  cylinder  =  .009139  times  Ibs.  pull  at  the  draw-bar. 


MACHINE  FRICTION. 


347 


TABLE  LXX. 
RESULTS  OF  FRICTION  TESTS— (Continued). 


Number. 

I.H.P. 

Dynamometer. 

Friction  in  Terms  of 

Actual 
Read- 
ing. 

Correc- 
tion 
(to  be 
added). 

Dyna- 
mometer 
Reading 
(cor- 
rected). 

D.H.P. 

Dyna- 
mometer 
Pull 
Equiva- 
lent to 
I.H.P. 

I.H.P. 

Per 
Cent  of 
I.H.P. 

Pounds 
Dyna- 
mometer 
Pull. 

Pounds? 
M.E.P. 

1 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

1 

2 
3 
4 
5 

6 
7 

8 

198.1 
185.7 
285.0 
285.6 
357.8 
321.3 
371.4 
396.1 

4,392 
3,936 
3,472 
3,449 
3,015 
2,681 
2,292 
1,799 

166 
133 
168 
133 
169 
141 
194 
205 

4,558 
4,069 
3,640 
3,582 
3,182 
2,822 
2,486 
2,004 

174.5 
163.2 
244.4 
245  .4 
302.4 
267.0 
309.5 
303.9 

5,177 
4,630 
4,245 
4,169 
3,764 
3,396 
2,983 
2,614 

23.6 
22.5 
40.6 
40.2 

55.4 
54.3 
61.9 

92.2 

11.95 
12.12 
14.25 
13.07 
15.46 
16.90 
16.66 
23.31 

619 
561 
605 

587 
582 
574 
497 
610 

5.66 
5.13 
5.53 
5.40 
5.33 
5.24 
4.49 
5.57 

9 
0 

1 
2 
3 

254.4 
371.4 
460.0 
495.6 
497.1 

6,045 
4,965 
4,188 
3,402 
2,524 

141 
151 
155 

184 
184 

6,186 
5,116 
4,343 
3,586 
2,708 

235.6 
340.1 
416.6 
445.3 
419.1 

6,678 
5,585 
4,796 
3,992 
3,212 

18.8 
31.3 
43.4 
50.3 

78.0 

7.38 
8.47 
9.43 
10.12 
15.65 

492 
469 
453 
406 
504 

4.50 
4.28 
4.14 
3.71 
4.61 

4 
5 

495.9 
582.0 

6,768 
5,424 

130 
134 

6,898 
5,558 

468.8 
544.4 

7,297 
5,939 

27.1 
37.6 

5.49 
7.31 

400 
381 

3.66 
3.48 

1.30 
2.08 

3.84 
3.98 
4.41 
4.35 

6 

7 

8 
9 
0 

1 

290.1 
266.6 

7,284 
6,416 

136 
141 

7,420 
6,557 

284.6 

257.7 

7,562 
6,784 

5.5 

8.9 

1.89 
3.33 

142 
227 

420 
435 
483 
476 

373.9 
358.0 
327.5 
245.1 

3,349 
3,193 
2,812 

1,978 

167 
135 
128 
130 

3,516 
3,328 
2,940 

2,108 

333.9 
316.6 
281.3 
199.9 

3,936 
3,763 
3,423 

2,584 

40.0 
41.4 
46.2 
45.2 

10.70 
11.62 
14.11 
18.42 

2 
3 
4 
5 
6 
7 
8 
9 

285.4 
298.5 
294.8 
303.2 
296.9 
284.9 
295.7 
276.1 

3,732 
3,617 
3,592 
3,580 
3,662 
3,472 
3,650 
3,225 

156 
130 
149 
144 
140 
137 
133 
130 

3,888 
3,747 
3,741 
3,724 
3,802 
3,609 
3,783 
3,355 

250.5 
250.7 
251.2 
252.8 
256.2 
242.4 
256.8 
236.9 

4,430 
4,462 
4,390 
4,466 
4,405 
4,242 
4,356 
3,910 

34.9 
47.8 
43.6 
50.4 
40.7 
42.5 
38.9 
39.2 

12.23 
16.01 
14.79 
16.62 
13.71 
14.91 
13.12 
14.19 

542 
715 
649 
742 
603 
633 
573 
555 

4.95 
6.53 
5.93 
6.78 
5.51 
5.7$ 
5.24 
5.07 

170.  A  Comparison  of  Results. — The  factors,  upon  which  the  loss* 
of  power  by  friction  in  the  machinery  of  a  locomotive  depends,  con- 
cern chiefly  the  lubrication  of  the  moving  parts.  If  a  viscous  oil' 
is  used  in  any  or  all  of  the  journals  it  should  be  expected  that  the- 
frictional  loss  will  be  greater  than  when  a  more  limpid  oil  is  used. 
Again,  with  a  given  lubricant  in  service,  the  coefficient  of  friction; 


348  LOCOMOTIVE  PERFORMANCE. 

is  affected  by  the  temperature  of  the  lubricant  and  of  the  metallic 
parts  surrounding.  Within  limits  which  are  rather  wide  the  friction 
'diminishes  as  the  temperature  of  the  lubricant  is  increased.  In  view 
£>f  these  facts,  therefore,  attempts  to  measure  frictional  loss  should 
not  be  expected  to  give  results  which  are  free  from  inconsistencies, 
isince  it  is  obviously  impracticable  to  control  the  temperature  of  all 
the  journals  of  a  locomotive,  or  even  the  precise  rate  at  which  lubri- 
cant is  supplied  them.  The  most  that  can  be  attempted  is  to  secure 
results  under  a  sufficient  number  of  different  working  conditions  to 
fairly  represent  the  ordinary  running  conditions  of  the  locomotive. 
Minor  inconsistencies  between  individual  results  must  be  expected. 

The  preceding  statements  will  naturally  suggest  the  fact  that  the 
operation  of  a  locomotive,  when  first  started,  is  attended  by  greater 
frictional  loss  than  after  its  parts  have  become  well  warmed  by  running. 
The  truth  of  this  statement  was  demonstrated  by  actual  test.  After 
being  at  rest  for  a  period  of  twenty-four  hours  the  Purdue  locomotive 
was  started  and  brought  to  a  speed  of  25  miles  an  hour,  with  the 
reverse-lever  in  the  first  notch  forward  of  center  and  the  throttle  fully 
open.  As  soon  as  possible  after  starting,  observations  necessary  to 
a  determination  of  the  frictional  loss  were  made,  and  were  thereafter 
repeated  at  five-minute  intervals  for  a  period  of  thirty  minutes,  after 
which  the  interval  between  observations  was  increased  to  ten  minutes, 
and  still  later  it  was  further  increased  to  twenty  minutes.  At  the 
end  of  the  first  ten  minutes  the  friction,  as  expressed  in  pounds  M.E.P., 
was  6J;  after  twenty  minutes  it  had  fallen  to  5.29,  after  which  the 
friction  fluctuated  by  small  amounts  both  above  and  below  this  value 
throughout  the  remainder  of  the  run,  which  was  continued  for  110 
minutes. 

Referring  to  Tables  LXIX.  and  LXX.  it  will  be  seen  that  all  tests 
<of  the  first  series  (Tests  1  to  8)  were  made  with  the  same  cut-off,  a 
constant  boiler  pressure,  and  a  fully  open  throttle.  Tests  in  dupli- 
cate at  speeds  approximating  15,  25,  and  35  miles  respectively, 
together  with  single  tests  at  speeds  of  47  and  57  miles,  are  included  in 
this  series.  The  duplicates  represent  the  work  of  different  days,  the 
purpose  being  to  show  whether  the  conditions  of  lubrication,  and, 
•consequently,  of  engine  friction,  vary  materially  from  day  to  day. 
'Comparing  the  results  derived  from  these  duplicates,  one  with 
•another,  by  means  of  values  given  in  Cols.  19  to  22,  it  will  appear 
that  differences  are  slight. 

A  study  of  the  whole  series  justifies  the  conclusion  that  frictional 


MACHINE  FRICTION.  349 

resistance,  as  shown  by  stress  in  the  draw-bar,  is  approximately 
constant  for  all  speeds,  being  equivalent  to  a  little  more  than  5  pounds 
mean  effective  pressure,  or  about  600  pounds  pull  at  the  draw-bar. 
As  measured  in  horse-power  the  frictional  loss  under  these  condi- 
tions increases  with  each  increase  in  speed. 

The  second  series  (Tests  9  to  13)  were  run  under  conditions  sim  lar 
to  those  of  the  preceding  group,  except  that  the  reverse-lever  was 
in  the  second  notch  from  the  center  forward,  giving  a  cut-off  of 
35  per  cent.  In  this  case,  also,  the  frictional  loss,  as  measured  by 
M.E.P.  or  by  draw-bar  stress,  is  practically  constant  for  all  speeds, 
but  its  value  is  numerically  less  than  when  the  cut-off  is  25  per  cent. 

The  third  series  (Tests  14  and  15)  show  the  same  progress  in  rela- 
tionship between  cut-off  and  friction  as  noted  for  the  previous  group, 
the  cut-off  in  this  case  being  very  nearly  half-stroke,  and  the  friction 
being  no  more  than  two-thirds  that  which  attends  operation  under 
a  cut-off  of  25  per  cent. 

The  fourth  group  of  values  (Tests  16  and  17)  was  obtained  with  the 
reverse-lever  in  the  ninth  notch  from  the  center,  giving  a  cut-off  of 
80  per  cent,  the  throttle  but  partially  open.  All  conditions  of  running 
were  the  same  for  both  tests,  except  that  in  Test  16  the  throttle-opening 
was  such  as  to  give  a  dry-pipe  pressure  of  81  pounds;  and,  in  Test 
17,  a  dry-pipe  pressure  of  73  pounds.  The  tests  are  very  nearly 
duplicates  of  each  other,  so  far  as  running  conditions  are  concerned. 
The  resultant  friction  is  lower  than  for  any  condition  previously  noted. 

The  series  embraced  by  Tests  18  to  21  also  represent  tests  run 
under  different  degrees  of  throttling.  In  this  case  the  reverse-lever 
was  in  the  second  notch,  making  the  cut-off  35  per  cent.  The  values 
for  frictional  resistance  (Col.  22)  are  nearly  constant,  though  they 
are  higher  than  those  obtained  from  either  of  the  tests  of  the  preced- 
ing group. 

Tests  22  to  29,  unlike  those  which  precede  them,  represent  data 
which  were  drawn  from  formal  efficiency  tests.  In  this  case  each 
value  is  the  average  of  from  fifteen  to  thirty  different  observations. 
When  compared  with  the  values  of  preceding  groups,  representing 
similar  conditions  of  running,  they  will  show  the  degree  of  coinci- 
dence in  the  results  secured  from  special  tests  and  those  which  are 
derived  from  the  more  formal  operation  of  the  plant. 

171.  Conclusions. — From  a  comparative  study  of  the  results  pre- 
sented in  Tables  LXIX.  and  LXX.  it  appears  that  when  the  cut-off 
remains  unchanged,  the  force  necessary  to  overcome  the  frictional 


350  LOCOMOTIVE  PERFORMANCE. 

resistance  of  the  machinery  of  a  locomotive  is  independent  of  speed. 
This  force  may  be  expressed  in  terms  of  mean  effective  pressure  or 
of  pull  at  the  draw-bar. 

The  experimental  results  make  it  evident,  also,  that  the  force 
necessary  to  overcome  the  friction  of  the  machinery  diminishes  as 
the  pressure  throughout  the  stroke  becomes  more  uniform.  As 
expressed  in  terms  of  the  data  it  diminishes  with  increase  of  cut-off. 
This  is  true  for  a  wide-open  throttle,  and  it  continues  to  be  true  when 
the  cut-offs  are  made  so  long  that  the  throttle  must  be  partially  closed 
to  avoid  exhausting  the  boiler.  With  a  given  dry-pipe  pressure  the 
force  necessary  to  overcome  the  frictional  resistance  is  evidently 
least  when  the  reverse-lever  occupies  an  extreme  position  upon  the 
quadrant.  All  of  these  facts,  as  they  apply  to  the  locomotive  experi- 
mented upon,  may  be  summarized  as  follows : 

When  the  reverse-lever  is  in  first  notch  (cut-off,  25%  of  stroke) , 
wide-open  throttle, 

the  frictional  resistance  =  5. 29  pounds  M.E.P. 

=  579        "       at  the  draw-bar. 

When  the  reverse-lever  is  in  second  notch  (cut-off,  35%  of  stroke), 
wide-open  throttle, 

the  frictional  resistance  =  4. 18  pounds  M.E.P. 

=  458        "      at  the  draw-bar. 

When  the  reverse-lever  is  in  third  notch  (cut-off,  45%  of  stroke), 
wide-open  throttle, 

the  frictional  resistance  =  3. 57  pounds  M.E.P. 

=  391        "      at  the  draw-bar. 

When  the  reverse-lever  is  in  ninth  notch  (cut-off,  80%  of  stroke), 
partially  open  throttle, 

the  frictional  resistance  =  1.69  pounds  M.E.P. 

=  185        "      at  the  draw-bar. 

With  the  force  necessary  to  overcome  the  frictional  resistance  of 
the  machinery  constant,  as  set  forth  above,  it  is  evident  that  the 
power  absorbed  in  friction  will  be  proportional  to  the  speed.  The 
facts  with  reference  to  the  horse-power  equivalent  of  the  machine 
friction  for  the  engine  tested  may  be  defined  as  follows: 


MACHINE  FRICTION.  351 

When  the  reverse-lever  is  in  first  notch  (cut-off,  25%  of  stroke), 
wide-open  throttle, 

machine  friction  expressed  in  horse-power  =  1. 39  X speed 
expressed  in  miles  per  hour. 

When  the  reverse-lever  is  in  second  notch  (cut-off,  35%  of  stroke), 
wide-open  throttle, 

machine  friction  expressed  in  horse-power  =  1. 24 X speed 
expressed  in  miles  per  hour. 

When  the  reverse-lever  is  in  third  notch  (cut-off,  45%  of  stroke), 
wide-open  throttle, 

machine  friction  expressed  in  horse-power  =  1. 04 X  speed 
expressed  in  miles  per  hour. 

The  preceding  statement  has  been  made  the  basis  from  which  to 
determine  a  correction  for  the  draw-bar  stress,  applying  to  the  data 
of  all  tests  run  prior  to  1896,  which  are  given  in  Chapter  IV.  For 
these  early  tests  the  draw-bar  stress  repo  ted  is  not  an  observed 
value,  but  one  which  has  been  thus  deduced. 


V.    LOCOMOTIVE  PERFORMANCE. 

CHAPTER  XX. 
THE  EFFECT  OF  THROTTLING. 

172.  Throttling. — A  locomotive  which  is  being  operated  under  a 
partially  closed  throttle-valve  is,  in  the  language  of  the  road,  being 
operated  under  the  throttle;  its  output  of  power  is  then  controlled  by 
the  position  of  the  throttle-valve.  For  operation  on  the  road  it  is 
necessary,  to  avoid  exhausting  the  boiler,  that  some  general  relation 
be  observed  between  the  position  of  the  reverse-lever  and  that  of  the 
throttle.  As  the  cut-off  is  reduced  by  hooking  up  the  reverse-lever, 
the  throttle-opening  may  be  increased.  This  fact  in  the  earlier  days 
led  to  many  discussions  among  locomotive  engineers  as  to  whether  it 
were  better  to  run  a  locomotive  with  a  long  cut-off  and  a  relatively 
small  throttle-opening  or  to  reverse  these  conditions.  As  to  the 
merits  of  the  discussion,  it  should  be  said  that  there  was  a  time  when 
the  machinery  of  locomotives  was  so  light  as  to  lend  color  to  the  belief 
that  the  locomotive  ran  better,  and  in  return  for  a  smaller  consump- 
tion of  fuel,  when  the  pressure  of  steam  admitted  to  the  cylinders 
was  much  below  that  of  the  boiler;  but  in  recent  years  locomotives 
have  become  better  designed,  and  practice  has  tended  steadily  toward 
the  wide-open  throttle.  In  so  doing  it  has  given  a  true  response  to 
well-known  thermodynamic  principles. 

While  correct  theory  points  to  the  desirability  of  admitting  steam 
to  the  cylinders  at  as  high  a  pressure  as  practicable,  the  losses  in  cylin- 
der efficiency,  resulting  from  a  20  or  30  per  cent  reduction  of  pres- 
sure by  throttling,  are  not  large.  This  is  due  to  the  fact  that 
in  wiredrawing  past  the  throttle  the  quality  of  the  steam  supplied 
the  cylinders  is  improved;  moist  steam  is  dried,  and  steam  which 
initially  is  dry  or  nearly  so,  may  be  superheated.  Because  of  this 
action  the  loss  resulting  from  the  drop  in  pressure  of  the  steam  is 
in  part  neutralized  by  the  rise  in  its  quality. 

352 


THE  EFFECT  OF   THROTTLING. 


353 


173.  The  Tests  designed  to  disclose  the  effect  of  different  degrees 
of  throttling  upon  the  economic  performance  of  the  engine  are  of  two 
groups.  The  first  group  of  nineteen  tests  represents  the  first  work 
undertaken  upon  the  Purdue  testing-plant.  These  tests  were  run  at 
a  time  when  the  experimental  character  of  the  plant  itself  required 
that  the  locomotive  be  worked  at  less  than  its  maximum  power.  The 
second  group  consists  of  three  tests  which  were  run  at  a  much  later 


DRAW- BAR  STRESS,  2600.POUNDS* 

©     ©     ©     ©     © 
©000© 


© 
© 


3  4  5  fi 

.Reverse  Lever,  Notch  from  Center 


=20 
=  15 


DRAW-BAR  STRESS,  5200  POUNDS. 

'©     ©   "©     © 
©     ©     © 


012345678  y 

Reverse  Lever,  Xotch  from  Center 

FIG.  208. — Conditions  Governing  Tests  under  the  Throttle. 

date,  the  results  of  which  are  recorded  in  Chapter  IV.*  Dealing 
first  with  the  tests  of  the  first  group,  the  conditions  of  speed  and 
cut-off  employed  are  defined  by  Fig.  208.  It  will  be  seen  by  this 
figure  that  the  tests  were  arranged  in  two  series,  for  which  the  draw- 
bar stress  was  constant  at  2600  pounds  and  5200  pounds  respectively. 

*  The  first  group  of  nineteen  tests  were  run  in  1892-93,  and  were  described  in 
detail  in  a  paper  entitled  "Tests  of  the  Locomotive  at  the  Laboratory  of  Purdue 
University,"  presented  to  the  American  Society  of  Mechanical  Engineers,  July, 
1893.  The  full  exhibit  of  data  from  these  tests  is  omitted  from  the  record  of 
Chapter  IV. 


354 


LOCOMOTIVE  PERFORMANCE. 


The  constant  draw-bar  stress  for  each  series  was  secured  for  the  several 
speeds  and  cut-offs  chosen  by  the  manipulation  of  the  throttle. 


,R.H.E. 


26.04 


R.H.E. 


27.46 


R.H.E. 


26.8 


R.H.E. 


27.9 


, 


RH.E. 


Test  No.l 
R.P.M.  81.6  Spring  80 


Test  No.2 
R.P.M.  79.3  Spring  60 


Test  No.  3 
R.P.M.  S0.6  Spring  60 


Test  No.4 
R.P.M.  79.2  Spring  60 


Test  No.  5 
R.P.M.  79.8  Spring  60 


Test  No.6 
R.P.M.  SO  Spring  60 


R.C.E. 


25.2 


R.C.E1. 


27.41 


R.C.E. 


25.8 


R.C.E. 


27.65 


27.41 


R.C.E. 


B.P. 
D.P.P. 


FIG.  209. 


174.  Indicator-cards. — Typical  indicator-cards,  resulting  from  the 
process  described,  are  given  as  Figs.  209,  210.  211,  and  212.  An 
inspection  of  the  cards  for  any  series  will  show  that  the  mean  effective 


THE  EFFECT  OF  THROTTLING. 


355 


pressure  is  practically  constant,  a  condition  growing  out  of  the  require- 
ment with  reference  to  a  constant  draw-bar  stress.    It  will  be  seen, 


H.H.E. 


Test  No.8 


Test  No.9 


Test  No.  10 


Test  No.  11 


FIG.  210. 


R.C.E. 


27.0 


30.6 


R.C.E. 


B.P. 
D.E.P. 


also,  that  the  degree  of  throttling  is  slight  for  the  shorter  cut-offs, 
and  that  it  increases  step  by  step  as  the  cut-off  is  lengthened,  until 
the  initial  pressure  is  but  a  small  fraction  of  that  of  the  boiler.  The 


356 


LOCOMOTIVE  PERFORMANCE. 


whole  group  of  tests  includes  four  series,  for  each  of  which  the  element 
of  progressive  throttling  appears  thus:  Under  a  draw-bar  stress  of 
2600  pounds,  a  series  at  15  miles  an  hour  and  another  at  25  miles  an 
hour;  under  a  draw-bar  stress  of  5200  pounds,  a  series  at  15  miles 
an  hour  and  another  at  25  miles  an  hour. 

175.  Numerical  Results  which  concern  the  present  purpose  are 
presented  as  Tables  LXXI.  and  LXXIL    The  test  numbers  of  these 


FIG.  211. 

tables  agree  with  the  numbers  of  Fig,  208,  and  also  with  the  numbers 
assigned  to  the  indicator-cards  in  Figs.  209  to  212.  The  boiler  pressure, 
Col.  7,  is  practically  constant  for  all  tests,  and  the  difference  between 
this  and  the  dry-pipe  pressure  (Col.  8)  may  be  accepted  as  a  measure 
of  the  degree  of  throttling  in  each  case.  By  Col.  9  it  will  be  seen  that 
when  the  power  developed  is  light,  the  steam  in  the  dome  of  the  boiler 
is  so  dry  that  it  becomes  considerably  superheated  in  passing  the 
throttle,  the  degree  of  superheating  increasing  as  the  difference  in 
pressure  upon  the  two  sides  of  the  throttle  is  increased.  As  the 
power  developed  becomes  greater,  the  quality  of  the  boiler  steam 
falls  and  the  superheating  effect  necessarily  diminishes.  The  failure 
of  the  steam  to  superheat  during  the  tests  of  highest  power,  however, 


THE  EFFECT  OF   THROTTLING. 


357 


is  in  part  to  be  accounted  for  in  the  lesser  degree  of  throttling  which 
occurs  in  these  tests. 

The  steam  consumption  per  horse-power  per  hour  (Col.  11)  shows 
the  extent  to  which  the  economy  of  the  engine  declines  with  each 
increase  of  the  throttling  action. 


Test  No.  18 
R.P.M.  131.5  Spring  80 


Test  No.  19 
R.P.M.  129.4  Spring  80 


FIG.  212. 

The  effect  of  throttling  upon  the  percentage  of  steam  used,  which 
is  shown  by  the  indicator,  is  given  in  Cols.  12  and  13,  and  in  this  con- 
nection it  is  of  interest  to  observe  that  the  percentage  of  steam,  which 
is  accounted  for  by  the  indicator,  is  increased  by  any  increase  in  the 
degree  of  throttling  or  in  the  period  of  admission.  Under  the  extreme 
conditions  covered  by  the  tests,  as  much  as  95  per  cent  of  all  the 
steam  supplied  the  cylinders  appears  in  the  record  of  the  indicator. 


358 


LOCOMOTIVE  PERFORMANCE. 


The  reevaporation  or  condensation  during  a  revolution  (Cols. 
15  and  16)  is  chiefly  affected  by  changes  in  cut-off.  As  the  cut-off 
is  lengthened,  the  period  of  expansion  is  diminished,  and  the  range 
of  temperature  to  which  the  walls  are  exposed  becomes  reduced,  so 
that  the  whole  process  of  heat  interchange  diminishes.  Moreover, 
since  these  changes  serve  to  shorten  the  expansion  curve,  the  period 
to  which  the  observations  apply  is  shortened,  all  of  which  serve  to 
explain  the  gradual  diminution  in  the  amount  of  reevaporation  and 
the  appearance  of  condensation  in  its  place. 

TABLE  LXXI. 
RESULTS  FROM  THROTTLING-TESTS. 


Steam 

Speed. 

Cut-off. 

Super- 

(by 

1 

Boiler 
Pres- 

Dry- 
pipe 
Pres- 

heat in 
Dry 
Pipe, 

I.H.P. 

Tank) 
I.H.P. 

pD 

Miles 

Notch 

Per 

sure. 

sure. 

Degrees 

per 

per 

R.P.M. 

from 

Cent  of 

F. 

Hour, 

£ 

Hour. 

Center. 

Stroke. 

Lbs. 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

I 

15.2 

81.60 

1 

18.6 

128.9 

104.4 

0 

128.4 

30.24 

1—  1 

2 

14.8 

79.30 

2 

26.9 

129.8 

76.0 

4 

128.5 

20.13 

SO 

3 

15.1 

80.59 

3 

36.2 

126.8 

62.0 

11 

128.1 

?1  ^8 

•§ 

4 

14.8 

79.18 

4 

46.7 

125.5 

48.6 

22 

117.7 

35.40 

OQ 

5 

14.9 

79.80 

5 

55.5 

128.7 

43.0 

24 

124.3 

36.67 

6 

14.9 

80.02 

9 

77.3 

129.7 

32.1 

35 

118.2 

47.07 

7 

23.8 

127.37 

1 

18.6 

128.4 

117.8 

0 

212.3 

28.97 

<M 

8 

24.0 

128.35 

2 

26.9 

129.6 

89.0 

0 

205.7 

29.18 

09 

9 

24.0 

128.47 

3 

36.2 

130.3 

70.0 

8 

209.9 

30.33 

"§ 

K) 

24.1 

128.77 

4 

46.7 

130.3 

58.9 

18 

220.6 

31.56 

OQ 

11 

23.9 

128.14 

5 

55.5 

127.7 

48.0 

22 

205.3 

37.06 

12 

23.9 

128.15 

9 

77.3 

129.7 

33.9 

31 

188.5 

44.62 

s 

13 

14.6 

78.20 

2 

26.9 

130.0 

126.1 

0 

222.9 

26.77 

M   CO 

14 

15.1 

76.42 

3 

36.2 

129.6 

97.3 

0 

224.8 

29.48 

£ 

1.5 

15.2 

81.13 

4 

46.7 

130.4 

89.2 

0 

244.5 

30.04 

TH 

16 

25.4 

136.04 

3 

36.2 

129.3 

118.0 

0 

399.5 

24.97 

» 

17 

24.4 

130.40 

4 

46.7 

130.2 

105.3 

0 

412.2 

27.57 

•g 

18 

24.6 

131.50 

5 

55.5 

128.0 

91.0 

0 

412.3 

29.62 

* 

19 

24.2 

129.37 

9 

77.3 

123.0 

79.3 

0 

392.5 

32.08 

176.  Steam  Consumption. — The  weight  of  steam  used  by  the 
locomotive  per  I.H.P.  hour,  when  developing  a  constant  amount  of 
power  under  different  degrees  of  throttling,  is  shown  by  Fig.  213,  the 
curves  of  which  are  plotted  from  the  values  of  Tables  LXXI.  and  LXXII. 
A  glance  at  this  figure  is  sufficient  to  show  that  throttling  effects  an 


THE  EFFECT  OF   THROTTLING. 
TABLE  LXXII. 

RESULTS   FROM  THROTTLING-TESTS—  (Continued). 


359 


Steam  (by 
Indicator) 

Per  Cent  of 
Mixture  in 

Per  Cent  of 
Live  Steam 

Reevaporation 
per 

Condensation 

£ 

per  I.H.P. 
per  Hour, 

Cylinder  Pres- 
ent as  Steam 

Condensed 
During 

Revolution. 

Revolution. 

6 

Approximate. 

at  Cut-off. 

Admission. 

* 

Lbs. 

Lbs. 

Lbs. 

1 

2 

13 

13 

14 

15 

16 

1 

17.50 

70 

42 

.0643 

0 

1—  1 

2 

19.76 

78 

30 

.0617 

0 

I 

3 

23.83 

81 

24 

.0272 

0 

I 

4 

28.93 

85 

18 

.0049 

0 

GO 

5 

31.08 

87 

15 

.0094 

0 

6 

42.8 

92 

13 

0 

.0193 

7 

17.85 

73 

39 

.0285 

0 

o? 

8 

20.72 

79 

29 

.0081 

0 

GO 

9 

23.65 

83 

22 

.0125 

0 

*c 

10 

26.2 

86 

17 

.0069 

0 

CO 

11 

30.38 

85 

18 

0 

.0045 

12 

42  22 

95 

9 

0 

.0193 

| 

13 

18.8 

75 

30 

.0111 

0 

FH  CO 

14 

20.42 

77 

26 

.0034 

0 

CO 

15 

24.00 

83 

16 

0 

.0004 

TH 

16 

20.67 

84 

20 

.0068 

0 

03 

17 

24.37 

88 

14 

0 

.0113 

*g 

18 

26.09 

89 

12 

0 

.0011 

1 

19 

29.00 

90 

10 

0 

.0036 

CURVES  SHOWING  STEAM   CONSUMPTION 

SJ.EAM  BY  TANK  80  REV.,  2600  LBS.   DRAW  BAR  STRESS  _^^__ 


IMD1SATOR     30 


CUT-OFF,  PER  CENT  OF  STROKE 


1st  N.   2nd  N. 


3rd  N. 


4th  N. 


1    60  I 

5th  N.   6th  N. 


9th  N- 


FIG.  213. 


360 


LOCOMOTIVE  PERFORMANCE. 


TABLE  LXXIII. 
RESULTS  FROM  THROTTLING-TESTS— (Continued). 


i 

Indicated 
Horse-power 

Tractive 
Horse-power. 

Friction  of 
Engine  in 
Horse-power. 

Friction  of 
Engine, 
Per  Cent  of 
Indicated 

Dynamometer 
Work  in  Foot  - 
tons  per  Pounu 
of  Steam  by 

3 

Horse  power 

Tank. 

fc 

1 

2 

17 

18 

19 

20 

21 

1 

128.38 

106.03 

22.35 

17.41 

26.90 

l-H 

2 

128.47 

103.05 

17.43 

14.47 

28.07 

CD 

3 

128.09 

104.72 

23.37 

18.24 

25.82 

*E 

4 

117.75 

102.89 

14.86 

12.62 

24.38 

OQ 

5 

124.30 

103.70 

20.60 

16.57 

22.45 

6 

118.21 

103.96 

14.25 

12.05 

18.49 

7 

212.37 

165.51 

46.85 

22.06 

26.63 

(N 

8 

205.70 

166.79 

38.91 

18.92 

27.50 

CO 

9 

209.93 

166.95 

42.97 

20.47 

25.96 

*c 

10 

220.61 

167.44 

53.17 

24.10 

23.58 

OQ 

11 

205.31 

166.52 

38.79 

18.89 

21.67 

12 

188.51 

166.52 

21.97 

11.65 

19.64 

y 

13 

222.90 

200.83 

22.06 

9.89 

33.33 

'C  eo 

14 

224.85 

209.28 

15.56 

6.92 

31.52 

1 

15 

244.56 

210.50 

34.06 

13.92 

28.64 

•* 

16 

399.48 

353.90 

44.09 

11  08 

33.53 

8 

17 

412.23 

338.36 

73.87 

17.92 

29.47 

18 

412.28 

341.19 

71.09 

16.90 

27.60 

c 

CO 

19 

392.51 

335.67 

56.84 

14.82 

26.37 

increase  in  the  consumption  of  steam,  the  extent  of  the  increase  under 
the  extreme  conditions  of  the  test  amounting  to  more  than  50  per 
cent.  It  is,  however,  noteworthy  that,  under  very  light  power,  a 
slight  amount  of  throttling  and  a  corresponding  lengthening  of  cut- 
off affects  the  economic  performance  of  the  engine  favorably.  The 
extent  of  this  favorable  influence  is  shown  in  the  upward  turn  of  the 
lower  end  of  the  upper  curve  (Fig.  213).  The  results  given  may  be 
accepted  as  a  fair  measure  of  the  engine  performance  under  different 
degrees  of  throttling  while  developing  constant  power.  With  refer- 
ence to  the  question  as  to  whether  the  engine  should  be  run  under 
the  throttle  or  by  the  reverse-lever,  they  furnish  direct  and  positive 
information. 

From  a  strictly  analytical  point  of  view,  however,  it  may  be  urged 
that  all  of  the  differences  in  effect  which  are  shown  should  not  be 
charged  against  the  throttling  action,  since,  as  the  throttling  action 


THE  EFFECT  OF   THROTTLING. 


361 


was  varied,  the  cut-off  also  was  changed.  From  this  point  of  view, 
the  curves  of  Fig.  213  may  be  regarded  as  showing  differences  in 
economy,  resulting  from  differences  in  cut-off  as  well  as  from  differ- 
ences in  the  degree  of  throttling.  The  data,  however,  permit  com- 
parisons between  tests  of  different  series,  which  may  be  so  selected 
that  the  cut-off  of  all  will  be  the  same.  Thus,  Tests  3,  9,  14,  and  16 
were  all  run  with  a  cut-off  of  approximately  35  per  cent,  an  efficient 
point  for  a  wide-open  throttle.  Such  a  comparison  is  shown  by 
Table  LXXIV.  which  follows,  from  which  it  appears  that  the  test 
having  the  least  amount  of  throttling  gives  the  most  economical 
performance.  Similar  comparisons  will  in  every  case  show  similar 
results. 

TABLE  LXXIV. 

EFFECT   OF  THROTTLING  AT  CONSTANT  CUT-OFF,   35  PER  CENT 

STROKE. 


Test  number 

3 

9 

14 

16 

Miles  per  hour 

15 

25 

15 

25 

Steam  per  I  H  P 

31  28 

30.33 

29.48 

24  97 

Dry-pipe  pressure  

62 

70 

97 

118 

Ratio  of  dry-pipe  pressure  to  boiler 

pressure  

.49 

.54 

.75 

.91 

Turning  now  to  the  second  group  of  throttling-tests,  results  of 
which  are  reported  in  Chapter  IV.  (Nos.  12,  20,  and  21),  it  will  be 
found  that  the  results  confirm  the  conclusions  already  drawn. 
These  tests  were  run  at  the  same  cut-off,  but  with  varying  degrees 
of  throttling,  a  summary  of  results  appearing  as  Table  LXXV. 

TABLE  LXXV. 


Boiler 
Pressure. 

Dry-pipe 
Pressure. 

Ratio  of  Dry- 
pipe  Pressure  to 
Boiler  Pressure. 

Steam  per  I.H.P. 
per  Hour. 

35-2-A 

131 

121 

.92 

26.28 

35-2-E 

128 

95 

.74 

27.92 

35-2-F 

155 

93 

.60 

27.18 

177.  Machine  Friction. — In  the  preceding  discussion  comparisons 
have  been  based  upon  the  indicated  horse-power.  Reference  to 
Table  LXXIII.  will  make  it  apparent  that,  for  the  development  of 
an  equal  amount  of  work,  frictional  losses  are  reduced  as  the  cut-off 


362  LOCOMOTIVE  PERFORMANCE. 

is  lengthened  and  the  throttle-opening  diminished.  One  effect  of 
throttling  is  to  reduce  engine  friction.  When,  therefore,  comparisons 
are  based  upon  the  work  of  the  draw-bar,  the  results  are  somewhat 
more  favorable  to  the  practice  of  throttling.  The  modifying  influ- 
ence, however,  of  reduced  friction  is  not  sufficient  to  affect  the  genera 
conclusion  already  stated. 


CHAPTER  XXI. 

EFFECT  OF  HIGH  STEAM  PRESSURES  ON  LOCOMOTIVE 
PERFORMANCE. 

178.  Power  and  Efficiency. — The  power  developed  by  a  locomo- 
tive is  a  function  of  boiler  pressure,  steam  distribution,  diameter 
and  stroke  of  piston,  and  of  speed.  The  efficiency  of  a  locomotive 
is  a  measure  of  the  degree  of  perfection  attending  the  development  of 
the  power;  broadly  stated,  it  is  the  ratio  of  the  heat  equivalent  of 
the  work  done  in  the  cylinders  to  the  heat  in  the  coal  supplied  to  the 
fire-box.  That  engine  is  most  efficient  which,  for  each  pound  of  coal 
burned,  develops  the  largest  amount  of  power  in  the  cylinders. 
Anything  which  affects  the  efficiency,  either  of  the  boiler  or  of  the 
engine  of  a  locomotive,  affects  the  efficiency  of  the  locomotive  as  a 
whole. 

The  maximum  power  which  can  be  developed  by  a  given  loco- 
motive depends  upon  the  power  capacity  of  the  several  elements 
making  up  the  complete  machine.  For  example,  any  increase  in  its1, 
capacity  for  burning  fuel  will,  other  things  being  equal,  increase  the- 
quantity  of  steam  delivered  from  the  boiler,  giving  an  increased  supply 
for  the  cylinders,  and  making  it  possible  for  them  to  develop  a  greater 
amount  of  power.  Similarly,  anything  affecting  the  efficiency  of 
the  several  transformations  between  the  grate  and  the  cylinder  affects 
the  maximum  output  of  power.  Thus,  any  increase  in  boiler  effi- 
ciency will  augment  the  amount  of  steam  delivered  for  a  given  weight 
of  coal  burned,  and  steam  thus  obtained  being  available  for  the  cylin- 
ders permits  a  higher  rate  of  power.  Again,  anything  which  promotes 
the  efficiency  of  the  cylinder  action  will  raise  the  maximum  limit  of 
power,  since,  with  a  constant  supply  of  steam  available,  the  most 
efficient  cylinder  action  will  result  in  the  delivery  of  greatest  power. 
There  is,  therefore,  a  double  purpose  gained  in  the  adoption  of  any 
change  in  design  or  practice  which  improves  the  efficiency  of  any 
material  part  of  the  locomotive.  If,  in  the  presence  of  such  a  change, 
the  output  of  power  remains  the  same,  then  the  increased  efficiency 

363 


364  LOCOMOTIVE  PERFORMANCE.  j 

implies  a  saving  in  fuel,  whereas,  if  the  same  quantities  of  fuel  are 
consumed,  then  the  increased  efficiency  implies  a  greater  output  of 
power. 

It  is  the  purpose  of  the  present  chapter  to  discuss  briefly  the  rela- 
tive advantage  of  different  steam  pressures  employed  in  locomotive 
service.  It  is  important  in  this  connection  to  note  that,  as  a  problem 
of  design,  increase  of  pressure  alone  does  not  raise  the  limit  of  power. 
But  if  it  can  be  shown  that  higher  pressures  improve  the  cylinder  action, 
then  their  adoption  will  result  in  a  saving  of  steam  which,  at  the  limit, 
may  be  made  to  appear  as  an  increase  of  power.  The  experimental  re- 
sults which  are  quoted  are  those  obtained  from  locomotive  Schenectady 
No.  1.  As  the  maximum  pressure  carried  by  this  locomotive  was 
but  140  pounds,  the  experiments  deal  with  what  is  now  to  be  regarded 
as  a  low  range  of  pressure.  The  discussion,  however,  may  take  a 
broader  view  and  the  conclusions  reached  will,  it  is  hoped,  soon  be 
confirmed  by  later  experiments. 

Steam  pressure  in  locomotive  service  has  been  gradually  increas- 
ing throughout  the  last  two  decades.  In  1890,  from  125  to  140  pounds 
were  common,  whereas,  at  this  writing,  pressures  commonly  range 
from  180  to  200  pounds,  and  a  few  locomotives  are  operating  using 
210  pounds.  The  term  "high  steam  pressure  "  at  this  time  may, 
therefore,  properly  apply  to  pressures  above  180  pounds. 

179.  Thermal  Advantages  of  High  Steam  Pressures. — Certain 
thermodynamic  facts  which  underlie  any  discussion  of  the  advan- 
tages of  high  steam  pressure  are  presented  as  Table  LXXYI. 

Cols.  I.  and  II.  show  the  relation  of  pressure  and  temperature, 
while  the  rise  of  temperature  for  equal  increments  of  pressure  is  found 
in  Col.  III.  It  is  evident  that  the  increased  temperature  for  pressures 
above  180  pounds  is  not  a  very  important  factor,  the  rise  from  180 
to  250  being  less  than  30  degrees.  Col.  IV.  shows  how  small  an  amount 
of  heat  is  required  to  be  added  to  steam  of  one  pressure  to  convert 
it  into  steam  of  a  higher  pressure.  The  cost  of  high-pressure  steam 
is  but  little  more  than  that  of  a  lower  pressure.  From  theoretical 
considerations  the  performance  of  a  perfect  engine  receiving  steam 
at  different  pressures  and  exhausting  against  a  back  pressure  of  13 
pounds  can  be  calculated.  The  results  of  such  a  calculation  are  pre- 
sented in  Cols.  VI.  and  VII.,  an  inspection  of  which  will  disclose  the 
gain  in  economy  resulting  from  each  increment  of  pressure.  The  fact 
should  be  emphasized  that  the  values  given  are  ideal;  they  may  be 
approached  but  never  equaled  by  an  actual  engine.  The  values 
are  important  as  showing  that  the  gain  for  equal  increments  of  pres- 


EFFECT  OF  HIGH  STEAM  PRESSURES 
TABLE  LXXVI. 


365 


I 

I 

£4 
I1 

1. 


25 
50 
75 
100 
125 
150 
175 
200 
225 
250 
275 
SCO 


II. 


266.6 
297.5 
319.8 
337.6 
352.7 
365.7 
377.3 
387.8 
397.3 
406.1 
414.2 
421.8 


o3-73 

Hi 

H^| 

.sis 


p  C  Q 

" 


III. 


30.9 

22.3 

17.8 

15.1 

13.0 

11.6 

10.5 

9.5 

8.8 

8.1 

7.6 


" 


c  a 


IV. 


1163.28 
1172.61 
1179.51 
1184.94 
1189.47 
1193.54 
1197.04 
1200.17 
1203.14 
1205.77 
1208.27 
1210.57 


31* 

c  a; 


SS 


V. 


9.33 
6.90 
5.43 
4.53 
4.07 
3.50 
3.13 
2.97 
2.63 
2.50 
2.30 


I 


VI. 


39.40 
26.25 
21.57 
19.53 
17.54 
16.45 
15.62 
15.00 

14!l7 
13.74 
13.39 


VII. 


36,888 
23,791 
19,227 
16,955 
15,185 
14,084 
13,242 
12,599 
12,067 
11,636 
11,255 
10,927 


'sfilp 

1        3M       £o3 


VIII. 


35.4 
19.1 
11.8 
10.4 
7.30 
5.97 
4.85 
4.22 
3.57 
3.27 
2.93 


sure  becomes  progressively  less  as  the  pressure  rises.  Between  175 
and  225  pounds  pressure  the  decrease  in  heat  consumption  becomes 
approximately  9  per  cent.  The  relation  between  steam  consumption 
of  the  perfect  engine  and  pressure  is  well  shown  by  Fig.  214,  which 
has  been  plotted  from  values  given  in  the  tables.  It  should  be  evident 
that,  as  practice  moves  up  in  the  scale  of  pressure,  the  chances  to 
save  by  resorting  to  still  higher  pressures  become  less  and  less. 

1 80.  The  Arguments  for  and  against  the  Use  of  Higher  Pres- 
sures may  be  summarized  as  follows: 

AGAINST  HIGHER  PRESSURES. 

1.  Increased  weight  of  boiler  due  to 
thicker  plates. 

2.  Increased  first  cost  of  boiler. 


IN  FAVOR  OP  HIGHER  PRESSURES. 

1.  Smaller  cylinders  and  consequently 
lighter  reciprocating  parts. 

2.  Reduced  width  of  engine  outside 
of  cylinders. 

3.  Reduced  first  cost  of  engine. 

4.  Reduced  transportation  charge  be- 
cause of  reduced  weight  of  engines. 

5.  A  possible  gain  in  the  efficiency  of 
the   engine,   whereby   a  given   power   is 
developed  on  less  steam  and  on  less  fuel 
than  could  have  been  done  with  a  lower 
pressure. 


3.  Increased     transportation     charge 
due  to  increased  weight  of  boiler. 

4.  Probable    increase    in    small    heat 
losses  from  radiation  and  from  leakage 
past  valves  and  glands. 

5.  Increased  difficulty  in  lubrication 
and  maintenance  of  packing  because  of 
higher  temperature  of  the  steam. 


366 


LOCOMOTIVE  PERFORMANCE. 


It  is  assumed  that,  other  things  being  equal,  the  evaporative  effi- 
ciency of  the  boiler  will  not  be  affected  by  such  modifications  in  its 
design  as  are  necessary  to  enable  it  to  withstand  the  increased  pressure, 
and  hence  the  efficiency  of  the  boiler  does  not  appear  on  either  side 
of  the  argument.  The  increased  weight  of  the  boiler  and  the  decreased 


300 


275 


c^p 


2-25 


200 


8 

£175 


150 


125 


100 


75 


I 


10 


15 


25  30          35 

Steam  per  l.H.P. 

FIG.  214. 


40 


45 


50 


5o 


weight  of  the  engines  are  not  very  considerable  factors  in  the  matter, 
and,  moreover,  they  tend  to  offset  one  another.  The  leakage  losses 
and  lubrication  difficulties  also  are  not  insuperable,  so  that  the  chief 
factor  in  this  discussion  becomes  the  expected  increase  in  the  economy 
of  the  engine. 

181.  Tests  at  Different  Pressures. — It  has  been  shown  in  the 
preceding  discussion  that  the  economy  of  a  perfect  or  ideal  engine 
increases  with  increase  of  pressure  according  to  the  curve  plotted  in 


EFFECT  OF  HIGH  STEAM  PRESSURES.  367 

Fig.  214.  An  actual  engine,  however,  may  or  may  not  show  a  similar 
increase,  although  it  has  generally  been  assumed  that  it  will.  The 
results  of  three  tests  at  different  pressures  made  upon  Schenectady 
No.  1  are  given  in  Table  LXXVII. 

Using  the  values  of  this  table,  points  have  been  plotted  through 
which  the  curve  ab  (Fig.  214)  has  been  drawn.  The  line  is  a  short 
one,  and  it  is  rather  difficult  to  determine  what  the  real  tendency 
may  be.  It  is  not  far  from  bearing  a  constant  relation  to  the  curve 
of  the  perfect  engine.  Assuming  that  this  indication  is  true,  and 
that  the  relation  continues  beyond  the  range  of  the  experiments,  the 
experimental  line  may  be  continued  to  the  point  c. 

The  relationship  is  important,  since  by  it,  if  the  steam  consumption 
for  an  actual  engine  is  known  for  any  one  pressure,  its  probable  per- 
formance for  all  other  pressures  may  be  definitely  calculated.  The 
location  of  curve  ab  shows  about  50  per  cent  greater  steam  consump- 
tion for  the  actual  engine  than  for  the  perfect  engine  within  the  limits 
of  the  experiments.  As  applied  to  the  case  in  hand  it  shows  that  a 
pressure  of  150  pounds  should  result  in  a  consumption  of  steam  per 
I.H.P.  per  hour  slightly  in  excess  of  24  pounds;  and  that  a  pressure 
of  300  pounds  should  bring  the  consumption  below  20  pounds. 

182.  Pressure  vs.  Capacity. — Thus  far,  consideration  has  been 
given  the  problem  of  increasing  the  power  of  a  locomotive  by  means 
of  higher  pressures.  Attention  may  now  be  given  the  problem  of 
securing  the  same  results  by  means  of  increased  boiler  capacity. 

Table  LXVIII.  gives  some  facts  concerning  weights  of  boilers  for 
various  pressures.  The  figures  in  Col.  II.  were  supplied  by  the  courtesy 
of  the  Baldwin  Locomotive  Works.  Col.  III.  gives  the  weight  of  the 
boilers  of  the  Purdue  locomotives,  Schenectady  Nos.  1  and  2,  which 
are  in  every  way  similar,  except  as  to  the  steam  pressure,  for  which 
they  were  designed.  From  the  values  it  will  be  seen  that  an  increase 
in  steam  pressure  from  150  to  240  pounds  in  a  60-inch  boiler 
necessitates  an  increase  in  weight  of  5900  pounds,  or  18  per  cent,  and 
that  an  increase  from  140  to  250  pounds  in  a  52-inch  boiler  necessitates 
an  increase  of  4700  pounds,  or  22  per  cent.  It  will,  therefore,  be 
sufficiently  accurate  for  the  present  purpose  to  assume  that  a  change 
of  pressure  from  150  to  240  pounds,  an  increase  of  90  per  cent, 
will  demand  an  increase  of  about  20  per  cent  in  weight  of  boiler. 

The  evaporative  efficiency  of  a  boiler  has  been  shown  to  depend 
on  the  rate  of  evaporation  at  which  it  is  worked.  For  Schenectady 
No.  1  the  relation  of  efficiency  to  rate  of  evaporation  is  shown  by 


368 


LOCOMOTIVE  PERFORMANCE. 


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1 

EFFECT  OF  HIGH  STEAM  PRESSURES. 


369 


TABLE  LXXVIIL 

SHOWING  CHANGE  IN  WEIGHT  OF  BOILER  WITH  STEAM    PRESSURE. 


Steam  Pressure. 

Weight  of  60-inch  Boiler. 

Weight  of  52-inch  Boiler. 

I. 

II. 

III. 

140 
150 

33,121 

21,035 

180 

35,253 

210 
240 

38,513 
39,035 

' 

250 

25,775 

the  line  de  of  Fig.  215.     It  will  be  seen  that  a  decrease  in  the  rate  of 
evaporation  increases  the  amount  of  water  evaporated  per  pound  of 


i: 

& 

.2s 

I4 
> 

W 


!, 


1          2          3         4          5          6          7         .8          9         10         11         12         13        14 
Equivalent  Evaporation  per  Square  Foot  of  Heating  Surface  per  Hour 

FIG.  215. — Evaporative  Performance. 

coal.  Thus,  suppose  that  at  a  certain  speed  and  load  the  boiler,  as 
at  present  designed,  is  required  to  evaporate  11.8  pounds  of  water 
per  square  foot  of  heating-surface  per  hour,  its  evaporative  efficiency 
will  be  that  represented  by  the  point  a.  For  the  present  purpose  it 
may  be  assumed  that  an  increase  of  20  per  cent  in  the  weight  of  the 
boiler  will  give  a  proportional  increase  in  the  extent  of  it?  heating- 
surface,  the  pressure  for  which  it  is  designed  remaining  unchanged. 


370 


LOCOMOTIVE  PERFORMANCE. 


On  this  assumption  the  boiler  with  20  per  cent  increase  in  weight 
would  at  the  same  power  be  compelled  to  evaporate  only  9.7  pounds 
of  water  per  square  foot  of  heating-surface,  and  its  efficiency  would 
rise  to  that  represented  by  the  point  c,  an  increase  in -efficiency  of 
about  11  per  cent.  This  increase  in  efficiency  is  due  wholly  to  the 
increased  capacity  of  the  boiler.  Numerical  values,  based  on  the 
assumption  that  increase  in  capacity  will  be  proportional  to  increase 
of  weight,  are  given  in  Table  LXXIX.,  from  which  it  will  be  seen  that 
any  increase  in  the  size  of  the  boiler  can  be  depended  upon  to  yield 
a  definite  return  in  the  improved  performance  of  the  locomotive. 

TABLE  LXXIX. 

SAVING  IN  FUEL  BY  USING  A  BOILER  THE  CAPACITY  OF  WHICH  IS 
GREATER  THAN  AN  ASSUMED  NORMAL  BOILER. 


Pounds  of  Water  required 
to  be  Evaporated  per 
Square  Foot  of  Heat- 
ing-surface   per   Hour 
in  a  Normal  Boiler. 

Percentage  Saving  in  Fuel  by  Using  a  Boiler  the  Capacity  of  which 
is  Greater  than  the  Normal  Boiler  by  5,  10,  15,  and  20  Per  Cent 
Respectively. 

5  Per  Cent. 

10  Percent. 

15  Per  Cent. 

20  Per  Cent. 

I. 

II. 

III. 

IV. 

V. 

5 

0.8 

1.5 

2.2 

2.9 

6 

1.0 

1.9 

2.8 

3.7 

7 

1.2 

2.3 

3.4 

4.5 

8 

1.5 

2.9 

4.1 

5.3 

9 

1.8 

3.4 

4.8 

6.1 

10 

2.0 

3.9 

5.5 

7.1 

11 

2.3 

4.5 

6.4 

8.2 

12 

2.7 

5.1 

7.4 

9.4 

13 

3.0 

5.7 

8.4 

10.7 

14 

3.4 

6.4 

9.4 

12.0 

15 

3.8 

7.4 

10.6 

13.6 

183.  Summary. — The  preceding  paragraphs  all  refer  to  a  simple 
cylindered  locomotive  using  saturated  steam.  They  give  evidence  to 
the  fact  that  locomotive  efficiency  can  be  increased  either  by  employing 
a  higher  pressure  or  a  larger  boiler,  and  some  data  are  presented 
tending  to  show  the  rate  of  change  in  each  case.  The  problem  in 
design  which  is  here  touched  upon  may  be  stated  as  follows:  When 
there  is  opportunity  to  increase  the  weight  of  a  locomotive  boiler  of 
a  given  class,  will  it  be  better  to  make  a  stronger  boiler  that  higher 
steam  pressure  may  be  carried,  or  a  larger  boiler  that  the  rate  of 
evaporation  may  be  reduced?  In  the  one  case  the  advantage  will 
appear  in  the  improved  performance  of  the  cylinders,  and  in  the 


EFFECT  OF  HIGH  STEAM  PRESSURES.  371 

other  in  the  higher  evaporative  efficiency  of  the  boiler.  The  variables 
in  the  problem  have  each  been  considered,  and  an  attempt  has  been 
made  to  estimate  their  value,  but  its  complete  solution,  which  will 
fix  limits  and  give  a  numerical  measure  of  the  benefits  to  be  derived 
as  the  result  of  definite  changes  along  either  line,  must  await  the 
accumulation  of  a  greater  array  of  facts  than  are  at  present  available.* 

*  Since  the  preparation  of  this  manuscript,  there  has  been  completed  at  the 
Purdue  Laboratory  (Aug.  1906),  under  the  patronage  of  the  Carnegie  Institution, 
an  elaborate  series  of  tests  to  determine  the  value  of  high  steam-pressures  in  loco- 
motive service.  Values  whicb  fairly  represent  the  consumption  of  steam  ID  pounds 
per  horse-power  hour  under  different  pressures  are  as  follows: 

Boiler-  Steam  per  I  H.  P. 

pressure.  per  Hour. 

120 29.1 

140 27.7 

160 26.6 

180 '. 26.0 

200 25.5 

220 25.1 

240 24.7 

Tests  were  run  under  the  several  pressures  given  at  different  speeds  and  cut-offs. 
The  values  quoted  do  not  represent  the  minimum  steam  consumption  nor  the  maxi- 
mum, but  are  those  which  have  been  determined  from  a  full  analysis  of  all  data. 
They  may  be  accepted  as  fairly  representative  of  the  performance  of  the  Purdue 
locomotive  under  normal  conditions  of  running.  A  summarized  statement  covering 
the  work  and  the  results  derived  therefrom  is  as  follows  : 

1.  The  results  apply  only  to  practice  involving  single-expansion  locomotives  using 
saturated  steam. 

2.  Tests  have  been  made  to  determine  the  performance  of  a  typical   locomotive 
when  operating  under  a  variety  of  conditions  with  reference  to  speed,  power,  and 
steam-pressure. 

3.  The  rate  of  change  in  efficiency  resulting  from  changes  in  steam-pressure   has 
been  established  by  the  results  of  carefully  conducted  tests.     They  show  that  the 
higher  the  pressure  the  smaller  the  possible  gain  resulting  from  a  given  increment 
of  pressure.     An  increase  of  pressure  from  160  to  200  pounds  results  in  a  saving 
of  1.1  pounds  of  steam  per  horse-power  hour,  while  a  similar  change  from  200 
to  240  pounds  improves  the  performance  only  to  the  extent  of  .8  of   a  pound  per 
horse -power  hour. 

4.  The  improvement  in  performance  with  increase  of  pressure  will  in  service 
depend  upon  the  degree  of  perfection  attending  the  maintenance  of  the  locomotive. 
The  values  quoted  in  the  preceding  paragraph  assume  a  high  order  of  maintenance. 
If  this  is  lacking,  it  may  easily  happen  that  the  saving  which  is  anticipated  through 
the  adoption  of  higher  pressure  will  entirely  disappear. 

5.  The  difficulties  to  be  met  in  the  maintenance  both  of  boiler  and  cylinders 
increase  with  increase  of  pressure. 


372  LOCOMOTIVE  PERFORMANCE. 

6.  A  simple  locomotive  using  saturated  steam  will  render  good  and  efficient  ser- 
vice when  designed  to  work  under  a  pressure  as  low  as  160  pounds;  under  most  favor- 
able conditions  no  real  advantage  is  gained  by  designing  for  pressures  greater  than 
200  pounds. 

7.  Wherever  the  water  which  must  be  used  in  boilers  contains  foaming  or  scale- 
making  admixtures,  the  pressure  for  best  results  should  not  exceed  180  pounds; 
where  feed- water  is  exceptionally  bad,  it  will  be  found  advantageous  to  fix  the  maxi- 
mum below  this  limit. 

8.  As  the  scale  of  pressure  is  ascended,  an  opportunity  to  further  increase  the 
weight  of  a  locomotive  should  in  many  cases  find  expression  in  the  design  of  a  boiler 
of  increased  capacity  rather  than  one  for  higher  pressures. 

9.  For  the  development  of  a  given  power,  any  increase  in  boiler  capacity  brings 
its  return  in  improved  performance  without  adding  to  the  cost  of  maintenance,  or 
opening  any  new  avenues  for  incidental  losses.     As  a  means  to  improvement,  it  is 
more  certain  than  that  which  is  offered  by  increase  of  pressure. 

10.  From  the  simple  standpoint  of  efficiency,  and  neglecting  all  questions  of 
maintenance  above  180  pounds,  it  is  better  to  utilize  any  allowable  increase  in  weight 
by  providing  a  larger  boiler  rather  than  to  provide  a  stronger  boiler  to  permit  higher 
pressures. 

11.  Pressures  designated  in  the  preceding  paragraphs  are  to  be  accepted  as  run- 
ning pressures.     They  are  not  necessarily  those  at  which  safety-valves  open. 

12.  The    preceding   statements   justify  the   conclusion   that  steam-pressures  in 
American  locomotive  service  have  already  been  carried    to    a    limit  which,  for  best 
results,  should  be  accepted  as   maximum. 


CHAPTER  XXII. 

CONCERNING  DIAMETER  OF  DRIVING-WHEELS. 

184.  Practice  with  Reference  to  Wheel  Diameters. — Prior  to  the 
renascence  of  the  American  locomotive,  which  had  its  beginning  in 
1894-95,  the  practice  of  this  country  was  committed  to  the  use  of 
driving-wheels  of  comparatively  small  diameter.     With  wheels  thus 
proportioned,  locomotives  were  very  effective  at  slow  and  moderate 
speeds,  but  at  high  speeds  the  rotation  reached  limits  which  were  not 
equaled  in  the  practice  of  other  countries.     Under  this  practice  the 
driving-wheels  of  fast  passenger  locomotives  were  driven  in  regulai 
and  ordinary  service  to  a  speed  of  between  300  and  400  revolutions 
a  minute;   while  a  rule  much  employed  by  a  prominent  builder  was 
to  make  the  diameter  of  the  drivers  in  inches  equal  to  the  speed  in 
miles  per  hour  for  which  the  locomotive  was  designed,  a  rule  which 
contemplates  a  speed  of  rotation  of  336  revolutions  per  minute. 

With  the  upbuilding  of  the  modern  American  locomotive,  driving- 
wheels  for  all  classes  of  service  have  been  materially  enlarged,  so  that 
in  ordinary  service  the  speed  of  rotation  is  now  not  so  high  as  for- 
merly, notwithstanding  which  fact  an  analysis  of  the  general  question 
will  not  be  without  interest. 

185.  A  Study  Based  upon  Observed  Facts. — From  the  data  and 
discussion  of  Chapter  V.,  it  is  evident  that  whenever  the  speed  of 
rotation  exceeds  the  critical  speed  a  loss  of  efficiency  results.     If, 
therefore,  high  train  speeds  are  demanded,  the  diameters  of  the  driving- 
wheels  should,  for  best  results,  be  so  proportioned  as  to  give  the 
desired  rate  of  travel  without  exceeding  the  critical  speed  of  rotation. 
The  following  illustration  will  serve  to  show  how  this  principle  may 
be  worked  out  hi  the  case  of  Schenectady  No.  1. 

The  proportions  of  the  locomotive  are  such  that,  neglecting  fric- 
tion, every  pound  of  mean  effective  pressure  exerted  in  the  cylinders 
will  produce  a  draw-bar  pull  of  109.4  pounds.  It  has  already  been 

373 


374  LOCOMOTIVE  PERFORMANCE. 

shown  (Chapter  V.,  paragraph  36)  that  the  power  of  this  locomo- 
tive becomes  maximum  when  the  speed  reaches  188  revolutions  per 
minute.  Examining  the  conditions,  first,  with  reference  to  a  cut-off 
of  35  per  cent,  it  will  be  found  that  the  mean  effective  pressure  at  this 
speed  is  42.4  pounds  (Test  35-2- A),  which  is  equivalent  to  a  pull  at 
the  draw-bar  of 

42.4X109.4  =  4639  pounds. 

If,  now,  it  is  required  to  operate  this  locomotive  at  a  speed  of  55 
miles  per  hour,  the  revolutions  must  increase  from  188  to  296  per 
minute,  which  will  cause  the  mean  effective  pressure  to  drop  to  27.4 
pounds  (Test  55-2- A).  This  makes  the  draw-bar  pull  at  55  miles 

27.4X109.4=2997  pounds. 

Suppose,  now,  that  instead  of  increasing  the  speed  of  rotation  from 
188  to  296,  the  diameter  of  the  driving-wheels  were  increased  from 
63  inches,  the  present  diameter,  to  99  inches,  a  diameter  which  will 
permit  a  speed  of  55  miles  an  hour  at  188  revolutions  per  minute. 
With  these  new  proportions  the  locomotive  would  give  but  69.4 
pounds  pull  at  the  draw-bar  for  each  pound  mean  effective  pressure. 
But  a  speed  of  55  miles  would  now  involve  only  188  revolutions  per 
minute,  and  the  mean  effective  pressure  would  be  42.4  pounds  (Test 
35-2- A),  which  would  give  a  pull  at  the  draw-bar  of 

42.4X69.4  =  2943  pounds, 

a  result  which  is  practically  identical  with  that  obtained  with  the 
smaller  wheels  and  a  higher  speed  of  rotation.  In  this  case,  therefore, 
there  has  been  no  loss  or  gain,  so  far  as  power  is  concerned  when 
operating  at  a  train  speed  of  55  miles  an  hour,  by  the  substitution 
of  99-inch  drivers  for  the  63-inch,  which  are  normal  to  the  engine. 

Since,  however,  the  engine  is  more  economical  in  its  use  of  steam 
at  the  critical  speed  than  when  the  revolutions  are  greater,  there 
would  be  some  gain  in  mechanical  action  through  the  use  of  the  larger 
driving-wheels,  since,  at  296  revolutions,  the  cylinders  require  32 
pounds  per  horse-power  hour,  while  at  188  revolutions  they  require 
but  26.3  pounds,  a  gain  of  21  per  cent. 

A  similar  comparison  based  upon  a  cut-off  of  25  per  cent  gives 
results  which  are  as  follows : 


CONCERNING  DIAMETER  OF  DRIVING-WHEELS.  375 

The  mean  effective  pressure  under  this  cut-off  is,  at  188  revolu- 
tions, 29.6  pounds,  and  at  296  revolutions,  18.3  pounds.  When  the 
train  speed  is  55  miles,  the  draw-bar  stress  with  the  present  63-inch 
driving-wheels  will  be 

18.3X109.4  =  2002  pounds. 

Whereas,  if  the  driving-wheels  were  increased  to  99  inches  the  draw- 
bar stress  would  be 

29.6X69.4  =  2054  pounds, 

which  is  a  gain  in  draw-bar  stress  in  favor  of  the  larger  wheels.  In 
this  case,  also,  there  would  be  an  increase  of  economy  resulting  from 
the  use  of  the  larger  wheels,  the  steam  consumption  under  the  con- 
ditions imposed  by  the  small  wheels  being  30.6  pounds,  and  under 
those  imposed  by  the  larger  but  27,  a  gain  of  13  per  cent. 

This  analysis  would  seem  to  establish  the  fact,  within  limits  that 
are  pretty  well  defined,  the  draw-bar  pull  at  speed  is  not  reduced 
by  increasing  the  diameter  of  the  wheels,  while  the  cylinder  action 
is  made  more  efficient.  Since,  in  the  case  of  a  locomotive,  anything 
which  saves  steam  may  at  the  limit  be  utilized  in  producing  more 
power,  the  benefits  in  increased  power  to  be  derived  from  an  increase 
in  the  diameter  of  driving-wheels  is  drawn  from  a  twofold  source. 

186.  A  Recapitulation  of  the  facts  of  the  analysis  which  has  been 
given  is  presented  in  Table  LXXX. 

It  is  admitted  that  there  are  mechanical  difficulties  to  be  over- 
come before  wheels  of  very  large  diameter  can  be  used,  also  that 
conditions  of  service  requ  re  some  sacrifice  of  efficiency  at  speed  to 
insure  satisfactory  performance  in  starting,  and  doubtless  in  many 
classes  of  service  such  considerations  fully  justify  the  use  of  the  smaller 
wheels.  The  purpose  is  not  to  condemn  practice,  but  to  show  what 
proportions  are  desirable  for  operation  at  speed. 

Finally,  in  this  connection  it  is  to  be  noted  that  the  modern  loco- 
motive has  been  given  wheels  which,  while  yet  too  small  for  highest 
efficiency  at  the  rates  of  speed  at  which  many  locomotives  are  driven, 
are  much  larger  than  those  which  were  used  in  the  early  ;90's,  when 
Schenectady  No.  1  was  built.  These  large-wheeled  engines  have 
proved  economical  in  the  use  of  water  and  coal. 


376 


LOCOMOTIVE  PERFORMANCE. 


TABLE  LXXX.* 

SHOWING  CERTAIN  RESULTS  OBSERVED  IN  CONNECTION  WITH 
LOCOMOTIVE  SCHENECTADY,  AND  SIMILAR  RESULTS  DEDUCED 
FROM  DATA  GIVEN  ON  THE  SUPPOSITION  THAT  THE  DIAMETER 
OF  ITS  DRIVING-WHEELS  HAD  BEEN  INCREASED  IN  THE  RATIO 
OF  35  TO  55.  SPEED  CONSTANT  AT  55  MILES  AN  HOUR.  THROT- 
TLE FULLY  OPEN. 


Present 

Drivers, 

63-inch 

Diameter. 


Proposed 
Drivers, 
99-inch 

Diameter. 


Revolutions  per  minute 

Approximate  speed  in  miles  per  hour 

Indicated  horse- power  (Table  I): 

6-inch  cut-off 

8-inch  cut-off 

Tractive  force,  pounds: 

6-inch  cut-off 

8-inch  cut-off 

Steam  per  indicated  horse-power  per  hour  (Table  III): 

6-inch  cut-off 

8-inch  cut-off 

Coal  per  indicated  horse-power  per  hour  (Table  IV): 

6-inch  cut-off 

8-inch  cut-off 

Gain  or  loss  in  indicated  horse-power  resulting  from  use 
of  99-inch  drivers  in  place  of  63-inch  drivers  for  speed  of 
55  miles  an  hour: 

6-inch  cut-off 

8-inch  cut-off 

Decrease  in  steam  consumption  resulting  from  use  of  99- 
inch  drivers  in  place  of  63-inch  drivers  for  speed  of  55 
miles  an  hour: 

6-inch  cut-off 

8-inch  cut-off 

Decrease  in  coal  consumption  resulting  from  the  use  of 
99-inch  drivers  in  place  of  63-inch  drivers  for  speed  of 
55  miles  an  hour: 

6-inch  cut-off 

8-inch  cut-off.  . 


296 
55 

292 
438 

1995 

2987 


188 
55 

298 
431 

2054 
2943 


30.6 
32.0 

5.12 
6.03 


26.9 
26.28 

4.18 
4.54 


Gain 2.9  per  cent 

Loss 1.4  per  cent 


12  per  cent 
18  per  cent 


18  per  cent 
23  per  cent 


*  This  table  and  the  arguments  based  thereon  were  first  presented  to  the  Western 
Railway  Club,  May,  1896. 


CHAPTER  XXIII. 
ATMOSPHERIC  RESISTANCE  TO  THE  MOTION  OF  RAILWAY  TRAINS. 

187.  Atmospheric  Resistance. — The  resistance  which  must  be 
overcome  by  a  moving  train  arises  from  several  causes,  as,  for  ex- 
ample, from  the  rolling  friction  of  wheel  on  rail,  the  effect  of  gradients 
and  curvatures  in  the  track,  the  necessity  of  producing  accelerations 
in  the  speed,  the  friction  of  journals,  and  the  resistance  of  the  atmos- 
phere. 

The  work  which  must  be  done  to  overcome  the  effect  of  grades 
and  to  produce  accelerations  in  speed  can  be  accurately  determined, 
and  the  value  of  journal  and  rolling  friction,  when  considered  apart 
from  complicating  conditions,  is  already  somewhat  definitely  known, 
but  the  available  evidence  concerning  atmospheric  resistance  is  con- 
tradictory and  the  result  of  its  application  uncertain.  This  fact 
makes  of  interest  certain  experiments,  which  were  conducted  at  the 
Engineering  Laboratory  of  Purdue  University  during  the  school  year 
1895-96  by  Professor  H.  C.  Solberg,  then  a  graduate  student  in  the 
laboratory.* 

The  conditions  under  which  experiments  were  made  were  assumed 
to  be  similar  to  those  surrounding  a  train  moving  through  still  air, 
and  the  object  of  the  experiments  has  been  to  disclose  the  value  of 
forces  resulting  from  the  resistance  offered  by  a  quiescent  atmosphere 

*  An  account  of  these  experiments  was  first  published  as  a  paper  before  the  West- 
ern Railway  Club,  April,  1896.  The  principal  references  given  were: 

"A  Study  of  Atmospheric  Resistance  to  the  Motion  of  Railway  Trains."  A 
thesis  by  H.  C.  Solberg,  B.S.,  M.E.,  '96. 

"A  Study  of  Air-currents  in  a  Rectangular  Conduit."  A  thesis  by  Augustus 
C.  Spiker,  B.S.,'96. 

"An  Investigation  of  the  Air-currents  about  a  Moving  Car  or  Train  of  Cars."' 
A  thesis  by  Norman  E.  Gee,  B.S.,  '96. 

377 


378  LOCOMOTIVE  PERFORMANCE. 

to  the  forward  movement  of   trains   through  it.     No  attempt  was 
made  to  consider  the  effects  resulting  from  oblique  or  other  winds. 

188.  The  Plan  of  the  Experiments  involved  a  rectangular  con- 
duit, within  which  a  current  of  air  having  any  desired  velocity  could 
be  maintained.  Within  this  conduit,  and  exposed  to  the  action  of 
the  air-currents,  small  dummy  or  model  cars  were  mounted.  Each 
model  was  connected  by  means  of  a  sensitive  dynamometer,  with  a 
suitable  base  so  arranged  as  to  indicate  the  value  of  any  force  tending 
to  displace  it  in  the  direction  of  its  length.  A  single  model,  or  any 
number  of  models  placed  in  order,  as  in  a  train,  could  be  employed 
in  any  given  experiment,  the  effect  of  the  wind  upon  each  car  being 
always  shown  by  the  indication  of  its  attached  dynamometer.  It  is 
evident  that,  as  a  matter  of  principle,  it  is  not  material  whether  the 
model  is  at  rest  and  the  air  is  moved  past  it,  or  the  air  still  and  the 
model  moved  through  it;  that  is,  if  the  velocity  of  movement  is  the 
same  in  each  case  the  value  of  the  reaction  between  the  wind  and 
model  will  be  the  same.  While  the  effect  of  the  actual  conditions 
surrounding  the  apparatus  employed  will  be  carefully  reviewed  in 
another  paragraph  (see  paragraph  203),  it  may  for  the  present  be 
assumed  that  effects  observed  under  the  conditions  of  the  experi- 
ments are  the  same  as  would  have  been  observed  had  the  model  cars 
been  caused  to  move  through  still  air.  Before  proceeding  the  details 
of  the  apparatus  employed  should  be  briefly  examined. 

189.  Conduit. — The  conduit  in  which  the  flow  of  air  was  main- 
tained  for   the   experiments  is  in  the  form  of  a   rectangular  tube 
20X20  inches  in  section  and  60  feet  in  length.     A  cross-section  is 
shown  by  Fig.  216.     The  lower  face  is  of  solid  wood;   the  upper,  also 
of  wood,  is  pierced  at  intervals  of  six  feet  by  good-sized  openings, 
through  which  one  may  reach  into  the  interior.     These  openings  are 
closed  by  tight-fitting  covers.     The  side  faces  of  the  conduit  consist 
of  large  panels  of  glass  set  in  wooden  frames.    The  glass  sides  expose 
to  view  the  whole  interior  of  the  conduit,  so  that  both  the  position 
of  the  model  cars  and  the  reading  of  their  dynamometers  can  readily 
be  seen  by  the  observer  on  the  outside.    The  conduit  is  practically 
air-tight,  the  joints  between  glass  and  wood  being  covered  with  glued 
strips  of  paper.     The  interior  surfaces  also  are  unbroken  from  end  to 
end,  and,  where  of  wood,  are  made  so  smooth  by  shellac  as  to  offer 
but  slight  resistance  to  the  passage  of  air  through  the  tube. 

190.  Air-supply. — The  conduit  is  connected  at  one  end  with  a 
No.  60  Sturtevant  blower,  the  opposite  end  being  open  to  the  labora- 


ATMOSPHERIC  RESISTANCE  TO  MOTION  OF  TRAINS.     379 

tory.  The  whole  apparatus  being  in  one  room,  the  duty  of  the  blower 
is  simply  that  of  circulating  the  air  of  the  room  through  the  tube, 
forcing  it  in  at  one  end,  and  allowing  it  to  discharge  at  the  other. 
The  blower  is  of  sufficient  power  to  produce  air-currents  in  the  con- 
duit having  a  velocity  of  100  miles  an  hour. 


Man-Hole  Cover 


Ol£ 


CROSS  SECTION  OF  BOX 
FIG.  216. 


FIG.  217. 


191.  The  Determination  of  the  Velocity  of  the  Air-currents.  — 

The  velocity  of  the  moving  air  within  the  conduit  was  determined 
by  use  of  instruments  in  the  form  of  Pitot's  tubes.*     These  were 

*  A  simple  form  of  Pilot  tube  is  shown  by  Fig.  217.  It  consists  of  two  small 
tubes,  having  ends  inserted  into  the  flowing  stream,  the  velocity  of  which  it 
is  desired  to  measure.  The  end  of  one  tube  is  shaped  to  face  the  flow  of  the 
stream,  while  that  of  the  other  is  normal  to  the  flow.  The  exposed  ends  of  the  tubes 
connect  with  a  U-shaped  glass  tube,  partially  filled  with  water  or  other  liquid.  It 
will  be  seen  that  as  both  sides  of  the  U  tube  are  in  connection  with  the  flowing 
stream,  the  difference  in  the  height  of  liquid  columns  in  the  U  tube  cannot  be  due  to 
the  pressure  of  the  flowing  stream,  but  must  result  from  the  motion  of  the  stream. 

The  relation  between  the  displacement  of  the  gauge  and  the  velocity  of  the 
flowing  stream  is  expressed  by  the  equation 


when  v  is  the  velocity  of  the  stream  in  feet  per  second,  and  h  the  difference  in  height 
of  the  gauge  columns  in  feet,  measured  in  terms  of  a  substance  having  the  same 
density  with  the  one  whose  velocity  is  to  be  determined. 

Many  experimenters  have  from  time  to  time  testified  as  to  the  accuracy  of 
this  method  of  measuring  velocities.  It  has  long  been  used  by  physicists  and  meteor- 
ologists, and  Professor  W.  S.  Robinson,  who  has  recently  employed  it  extensively 
in  determining  the  flow  of  natural  gas  in  pipes,  states  that  he  was  able  to  check  his 
results  with  those  obtained  from  meters  with  a  satisfactory  degree  of  certainty. 

In  the  present  experiments  water  was  used  in  the  U  tubes,  and  the  relation 


380 


LOCOMOTIVE  PERFORMANCE. 


made  up  of  two  brass  tubes,  arranged  within  a  larger  tube  or  jacket, 
all  being  cemented  together  by  resin,  which  filled  the  interior  of  the 
jacket  around  the  smaller  tubes.  The  interior  diameter  of  the  small 
tubes  was  a  sixteenth  of  an  inch,  and  the  diameter  of  the  jacket-tube 
somewhat  less  than  a  half-inch,  while  the  length  of  the  combination 
was  such  as  made  it  possible  to  reach  from  the  ex- 

!^X    s~t 

terior  to  'any  portion  of  the  interior  of  the  conduit. 
This  portion  of  the  apparatus  is  shown  by  Fig.  218. 
When  in  use  the  tip  end,  a,  of  the  gauge  was  in- 
serted into  the  current  through  holes  bored  in  the 
top  planking,  a  cork  bushing  lining  the  hole,  and 
making  tight  the  joint  between  the  wood  and  the 
gauge.  Each  of  the  two  small  brass  tubes  making 
up  a  gauge  was  then  connected  by  rubber  tubing 
with  one  side  of  a  glass  U  tube  fixed  to  a  suitable 
scale  outside  of  the  conduit.  The  U  tubes  were 
sealed  with  water,  from  the  displacement  of  which 
.B  the  velocity  of  the  air  passing  the  tips  of  the  gauge 
was  determined.  Five  such  gauges  with  all  their 
connections  are  shown  in  place  in  the  conduit  by 
Fig.  219. 

,  ..  ,  The  several  gauges  employed  were  subjected  to  a 

careful  examination,  involving    a    series    of    simul- 
taneous observations  in  connection  with  a  systematic 
interchange   of   position,  to   determine  whether   all 
could  be  depended  upon  to   give   like  indications 
when  the  conditions  were  the  same. 
Another  preliminary  to  the  main  investigation  wras  that  of  deter- 
mining the  relative  velocity  of  the  stream  of  air  at  different  points 
in  the  cross-section  of  the  conduit.     This  was  done  by  dividing  the 


,-, 

r  IG. 


between  the  density  of  water  and  air  is  such  as  to  make  a  column  of  water  one  inch 
high  the  equivalent  of  a  column  of  air  68.37  feet  high.  The  equation  therefore 
becomes 

v2=  (2  X  32.2  X  68.37  )h=U03h, 

where  v  is  the  velocity  in  feet  per  second  and  h  is  the  head  in  inches  of  water.  If, 
therefore,  the  U  tube  of  a  gauge  used  in  the  experiment  showed  a  displacement  of 
an  inch  and  a  half,  the  velocity  of  the  air  passing  the  tips  of  gauge  in  feet  per  second 
was  assumed  to  be 

v=\/4403X  1.5=  81.2. 


ATMOSPHERIC  RESISTANCE  TO  MOTION  OF  TRAINS.    381 

cross-section  into  twenty-five  or  more  imaginary  squares,  and  by  ob- 
serving the  velocities  at  the  center  of  several  of  them  at  the  same  in- 
stant, after  which  some  of  the  gauges  were  changed  to  other  squares 
and  the  process  repeated,  the  observations  for  each  set  of  readings 
overlapping  those  of  the  preceding  set  as  a  check  on  the  constancy 
of  conditions.  A  number  of  typical  diagrams  resulting  from  this 
process  are  presented  as  Fig.  220.  They  show  velocity  of  the  cur- 


FIG.  219. 

rent  in  miles  per  hour  for  different  portions  of  the  cross-section  of  the 
conduit. 

That  there  might  be  no  uncertainty,  also,  as  to  the  character  of 
the  flowing  current  of  air,  the  cross-section  of  the  stream  was  care- 
fully examined  at  many  points  throughout  the  length  of  the  conduit, 
and  as  a  result  the  following  conclusions  were  reached: 

1.  That  while  considerable  unevenness  of  flow  was  observed  near 
the  initial  end  of  the  conduit  the  eddies  disappeared  at  a  distance  of 
35  feet  from  the  initial  end,  and  from  this  point  to  a  point  near  the 


382 


LOCOMOTIVE  PERFORMANCE. 


discharge  end  of  the  conduit  the  flow  was  found  to  follow  lines  which 
were  approximately  straight. 

2.  That  the  glass  surfaces  forming  the  sides  of  the  conduit  offered 
less  resistance  to  the  movement  of  the  air  than  the  wooden  surfaces 
forming  the  top  and  bottom. 

3.  That  the  lowest  velocities  were  found,  as  would  be  expected, 
in  the  corners  of  the  conduit,  that  is,  where  the  sides  joined  with  the 
top  and  bottom. 


Wood 


1  

21 

23 

24 

23 

21 

25 

29 

29 

29 

25 

25 

29 

29 

29 

25 

25 

28 

29 

29 

25 

21 

23 

25 

23 

21 

Wood 


47 

53 

53 

53 

46 

54 

61 

61 

61 

54 

55 

61 

61 

61 

55 

55 

61 

61 

61 

54 

46 

52 

53 

52 

47 

Wood 


Wood 


Wood 


80 

95 

95 

96 

81 

96 

100 

100 

100 

96 

96 

100 

100 

100 

96 

96 

100 

100 

100 

96 

81 

95 

95 

95 

81 

Wood 
FIG.  220. — Relative  Velocities  in  Different  Portions  of  the  Conduit. 

4.  That  there  was  a  comparatively  large  vein  in  the  interior  of 
the  stream,  all  portions  of  which  flowed  with  practically  the  same 
velocity. 

The  experiments  which  are  to  be  described  made  use  of  that  por- 
tion of  the  stream  which  was  most  free  from  eddies,  and  which  was 
least  influenced  by  the  walls  of  the  conduit". 

192.  The  Model  Cars. — Having   obtained   means   for   making   a 


ATMOSPHERIC  RESISTANCE  TO  MOTION  OF  TRAINS.    383 

breeze  of  satisfactory  quality  and  for  determining  its  velocity,  the 
next  and  last  step  concerned  the  model  cars  which  were  to  be  exposed 
to  its  influence.  To  facilitate  the  description  these  model  cars  will 
hereafter  be  referred  to  as  models.  These  were  &  the  size  of  an 
assumed  standard  box  car,  the  body  of  the  model  extending  down- 
ward and  occupying  the  space  which  in  an  actual  car  intervenes 


SECTION  ON  A-3 


SECTION  ON  C-D 


FIG.  221. 


between  the  sills  and  the  rails.  Each  model  was  12^r  inches 
long,  3J  inches  wide,  and  4£  inches  high.  Its  form  may  be  more 
perfectly  apprehended  by  reference  to  the  drawing  (Fig.  221). 
The  painted  tin  body  of  the  model  was  fitted  over  a  wooden  base 
supported  by  four  leg-pieces  of  light,  hard-rolled  sheet  brass  S, 
which  in  turn  were  securely  fastened  to  a  suitable  foundation. 


384  LOCOMOTIVE  PERFORMANCE. 

The  length  and  lightness  of  these  legs,  or  springs,  allowed  the  car  to 
be  displaced  longitudinally,  under  the  action  of  the  slightest  force, 
and  they  were  at  the  same  time  so  proportioned  as  to  resist  all  ten- 
dency to  motion  in  other  directions.  Between  the  body  of  the  car 
and  its  foundation,  also,  and  entirely  independent  of  the  springs 
already  referred  to,  was  a  system  of  levers,  the  purpose  of  which  was 
to  multiply  any  longitudinal  displacement  to  which  the  model  might 
be  subject.  These  levers  were  made  of  thin  metal,  the  several  parts 
being  soldered  to  each  other.  All  motion,  consequently,  was  within 
the  elastic  limit  of  the  parts  affected.  There  were  no  loose  joints. 
The  whole  arrangement  proved  to  be  both  sensitive  and  reliable. 
The  least  pressure  upon  the  car  would  result  in  a  movement  of  the 
pointer,  and  the  pointer  would  promptly  return  to  its  zero  when  the 
force  producing  the  displacement  had  ceased  to  act.  Excessive 
vibrations  of  the  pointer  were  prevented  by  a  vertical  fin  which  could 
be  made  to  dip  into  light  oil  contained  in  a  suitable  pan  beneath. 
That  no  part  of  the  dynamometer  might  be  directly  affected  by  the 
currents  of  air  acting  upon  the  model,  the  mechanism  was  en- 
tirely enclosed  in  the  foundation,  a  portion  of  the  surface  of  which 
was  of  glass  through  which  the  movement  of  the  pointer  could  be 
observed. 

The  degree  of  refinement  attending  the  action  of  these  dynamom- 
eter cars  will  be  appreciated  when  it  is  said  that,  while  the  actual 
movement  of  the  car  was  always  slight,  the  leverage  was  such  that  an 
inch  and  a  quarter  movement  of  the  pointer  was  readily  obtained. 
The  springs  for  a  number  of  cars  were  made  so  flexible  as  to  give  an 
inch  movement  of  the  pointer  under  the  force  of  one  ounce  acting 
upon  the  end  of  the  model.  Two  models,  however,  to  serve  at  the 
ends  of  trains,  were  provided  with  much  stiffer  springs. 

The  foundations  were  longer  than  the  models,  so  that  when  arranged 
in  trains  the  proper  spacing  of  models  would  be  observed,  while  the 
foundation  would  present  an  unbroken  surface.  Sections  of  blank 
foundation,  also,  were  supplied  in  front  and  rear  of  train.  A  draw- 
ing showing  a  train  of  three  cars  arranged  in  the  conduit  is  shown 
by  Fig.  222,  and  a  front  view  of  a  train  taken  from  within  the  conduit 
is  given  as  Fig.  223. 

193.  Observations. — With  the  desired  number  of  models  arranged 
as  a  train,  and  with  a  single  Pitot  tube  located  at  A  (Fig.  222),  which 
alone  was  used  in  determining  velocities  in  the  conduit,  the  experi- 
ments proceeded  about  as  follows :  The  blower  engine  was  started  and 


ATMOSPHERIC  RESISTANCE   TO  MOTION  OF   TRAINS.    385 

allowed  to  run  at  a  slow  speed  for  a  sufficient  time  to  secure  con- 
stancy of  conditions  with  the  conduit,  after  which  readings  were  taken 
simultaneously  from  the  gauge  A  and  the  dynamometers  of  the 
several  cars  composing  the  train.  These  observations  were  repeated 
at  intervals  of  thirty  seconds  until  five  readings  had  been  taken,  when 
the  averages  of  the  five  sucessive  readings  were  brought  forward  to 
a  condensed  log  of  observation.  When  one  set  of  readings  had  been 
taken,  the  speed  of  the  blower  was  increased,  and  all  observations 
made  for  the  new  conditions.  In  this  manner  the  work  was  advanced 
with  each  length  of  train,  the  velocities  of  the  air-currents  varying 
from  20  miles  per  hour  to  something  over  100  miles  per  hour.  No 
effort  was  made  to  obtain  definite  conditions  of  air-velocity,  the 


Car 


Car 


Car 


Cat 


Car 


Arrangement  of  Pitots  Tubes  and  Cars  in  Ho 


JB 

-<^_ 

« 

Car 

Car 

Car 

Car 

Car 

* 

THE  IRON  TRADE  REVIEW 


FIG.  222. — Side  View  of  Train  in  Conduit. 


object  being  to  have  a  constant  flow,  and  to  observe  accurately  what 
were  the  precise  values  by  which  the  conditions  were  defined. 

The  work  extended  through  several  weeks,  and  the  care  taken 
throughout  its  progress  was  such  that  the  data  are  remarkably  con- 
sistent. Tables  LXXXI.  to  LXXXVL,  which  are  given  herewith,  are 
somewhat  changed  in  form,  and  are  much  condensed  from  the  very 
elaborate  presentation  by  Professor  Solberg. 

194.  Observed  and  Calculated  Results. — The  significance  of  the 
seven  different  headings  appearing  in  the  several  tables  accompany- 
ing may  be  explained  as  follows : 

I.  Gauge  Displacement,  Inches  of  Water. — Values  in  this  column 
are  results  obtained  from  direct  readings  of  the  U  tube  gauges  con- 
nected with  the  Pitot  tubes.  They  represent  pressures  measured  in 
inches  of  water,  due  to  the  velocity  of  the  air-currents  within  the 
conduit. 


386 


LOCOMOTIVE  PERFORMANCE. 


II.  Pressure  Equivalent  of  Gauge  Displacement  in  Pounds  per  Square 
Foot. — These  values  are  calculated  directly  from  those  of  the  preceding 
column,  on  the  assumption  that  a  cubic  foot  of  water  weighs  62.3 
pounds.  Thus,  a  column  of  water  an  inch  high  is  the  equivalent  of 


1X62.3 
12 


=  5.19  pounds  per  square  foot, 


FIG.  223. 


so  that  the  values  of  Col.  II.  are  equal  to  those  given  in  Col.  I. 
tiplied  by  5.19.  The  values  given  in  this  column  will  be  found  useful 
for  purposes  of  comparison,  since  wind  pressures  are  usually  meas- 
ured in  pounds  per  square  foot. 

III.  Pressure  by  Gauge,  Multiplied  by  the  Area  of  the  Cross-section 
of  the  Model  in  Square  Feet.  —  In  general,  this  would  be  expected  to  give 
the  force  with  which  the  wind  would  act  upon  the  end  of  a  model. 
The  cross-section  of  each  model  was  equal  to  14  square  inches,  or 


ATMOSPHERIC  RESISTANCE  TO  MOTION  OF  TRAINS.    387 


TABLE  LXXXI. 

ONE   MODEL. 


Number 
of  Test. 

Gauge 
Displace- 
ment, 
Inches  of 
Water. 

•gag 

<5  «  a 

Ija  . 

ifil 

w*s 

*sP 

£«!" 

iPls 
l&£! 

?tual  Force  Tending 
to  Displace  Model, 
as  Shown  by  Model 
Dynamometer  in 
Pounds. 

il°2~ 

^.fe§5 

$«^«6 

loB^ 

•s'srl 

o  MO  £13 

•^.SSAH> 

Velocity  Calculated 
from  Reading  of 
Gauge. 

Feet  per 
Second. 

Miles  per 
Hour. 

£ 

£ 

3 

(5 

i. 

II. 

III. 

IV. 

V. 

VI. 

VII. 

1               0.3 

1.6 

.15 

.094 

.61 

36 

25 

2 

0.8 

4.2 

.40 

.219 

.54 

60 

41 

3 

2.6 

13.5 

1.31 

.625 

.48 

107 

73 

4 

3.8 

19.7 

1.91 

.906 

.47 

130 

88 

5 

5.0 

26.0 

2.52 

1.250 

.49 

149 

102 

TABLE  LXXXII. 
TWO  MODELS 


fa 

If! 

llr°? 

Velocity  Cal- 

. 

£  3 

>  a  <n 

O    K.  .2    83 

culated  from 

1 

l! 

ll§l 

*ili 

Actual  Force  Tending 
to  Displace  Model,  as 
Shown  by  Model  Dy- 

Ratio  of  Force  Tending 
to    Displace    Models 
(Col.  IV)  to  Pressure 

Reading  of 
Gauge 

Number  < 

|| 

0 

?««  2  cr 

j§^  Sao 

£ 

Pressure 
Multip 
of  Cro 
Model  i 

namometer       in 
Pounds. 

Due  to  Velocity  (Col. 
III). 

Feet 
Second 

Miles 
Hour. 

I—  T 

IV. 

V. 

T7TT 

. 

xL 

First 

Second 

Both 

First 

Second 

Both 

i. 

VII. 

Model. 

Model 

Models. 

Model 

Model. 

Models 

1 

0.3 

1.6 

.15 

.047 

.031 

.078 

.31 

.21 

.52 

36 

25 

2 

1.0 

5.2 

.50 

.200 

.078 

.278 

.40 

.15 

.55 

66 

45 

3 

2.1 

10.9 

1.06 

.438 

.150 

.588 

.41 

.14 

.55 

96 

66 

4 

2.8 

14.6 

1.42 

.563 

.172 

.735 

.40 

.12 

.52 

111 

76 

5 

5.4 

28.0 

2.72 

1.094 

.328 

1.422 

.40 

.12 

.52 

154 

105 

388 


LOCOMOTIVE  PERFORMANCE. 


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•W^nN                            „.„.,, 

ATMOSPHERIC  RESISTANCE  TO  MOTION  OF  TRAINS.     389 


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390 


LOCOMOTIVE  PERFORMANCE. 


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ATMOSPHERIC  RESISTANCE   TO  MOTION  OF   TRAINS.    391 


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392  LOCOMOTIVE  PERFORMANCE. 

.097  of  a  square  foot,  and  as  the  pressure  per  square  foot  is  given  by 
Col.  II.,  the  values  of  Col.  III.  are  found  by  multiplying  those  of 
Col.  II.  by  .097. 

IV.  Actual  Force  in  Pounds  Tending  to  Displace  Model,  as  Shown 
by  Model  Dynamometer. — In  all  excepting  Table  LXXXI.  more  than 
one  column  appears  under  this  numeral.     The  values  are,  in  every 
case,  those  which  have  resulted  from  direct  readings  of  the  model 
dynamometer.     When  compared  with  those  of  Col.  III.  they  sho\v 
the  effect  of  the  form  of  the  model  in  modifying  the  pressure  resulting 
from  the  moving  current  of  air  when  a  single  model  is  involved,  or 
the  effect  of  its  position  in  the  train  when  several  are  employed. 

V.  Ratio  of  Actual  Forces  Tending  to  Displace  Model,  or  Models, 
to  Pressure  Due  to  Velocity. — These  values  are  obtained  by  dividing 
the  several  values  given  under  IV.  by  the  corresponding  values  given 
in  Col.  III.     They  represent  the  fraction  of  the  pressure  due  to  the 
velocity  of  the  moving  air,  which  appears  as  an  actual  force  tending 
to  displace  the  several  models. 

VI.  Velocity  of  Air-currents   Calculated  from  Gauges  in   Feet  per 
Second. — The  velocities  were  calculated  by  use  of  the  equation 

v2= 4403ft, 

where  v  is  the  velocity  in  feet  per  second,  and  h  is  the  displacement 
of  the  water  in  the  gauge  measured  in  inches.* 

VII.  Velocity   of  Air-current    Calculated  from  Reading  of   Gauge 
in  Miles  per  Hour. — These  values  are  deduced  directly  from  those  of 
the  preceding  column. 

195.  One  Model. — The  effect  of  a  current  of  air,  impinging  directly 
upon  the  end  of  a  single  model,  may  be,  assumed  to  represent  the 
sum  of  three  partial  effects:  (1)  The  effect  of  the  direct  action  due 
to  the  exposure  of  the  initial  end  of  the  model;  (2)  the  effect  of  fric- 


*  It  may  be  noted,  also,  that  if  the  velocity  is  expressed  in  miles  per  hour,  and 
the  head  in  terms  of  pressure  in  pounds  per  square  foot,  this  equation  may  readily 
be  reduced  to 

P=.0025F2, 

which,  therefore,  like  the  equation  to  which  this  note  refers,  expresses  a  general 
relationship  existing  between  velocity  of  air  and  resulting  pressure.  The  equation 
is  one  often  proposed  and  sometimes  used  as  a  means  for  determining  wind  pres- 
sures on  structures,  but  the  form  of  structures  so  modifies  the  pressure  effects  pro- 
duced by  wind  that  the  equation  is  really  useful  only  for  the  purpose  of  determining 
velocities. 


ATMOSPHERIC  RESISTANCE  TO  MOTION  OF  TRAINS.    393 

tional  action  along  the  sides  and  top  of  the  model;  and  (3)  the  effect 
of  diminished  pressure,  or  "suction,"  at  the  rear  of  the  model. 

It  is  significant  that  the  numerical  value  of  the  sum  of  these  effects 
upon  the  model  is  much  less  than  the  calculated  value  based  upon 
the  cross-section  of  the  model,  and  the  indications  of  the  pressure- 
gauge.  Thus,  by  Table  LXXXI.  the  first  test  shows  that  the  gauge 
displacement  (Col.  I)  was  .3  of  an  inch,  which  is  equivalent  to  a  pres- 
sure per  square  foot  of  1.6  pounds  (Col.  II)  or  to  a  pressure  of  0.15  of 
a  pound  upon  an  area  equal  to  that  of  the  cross-section  of  the  model 
(Col.  Ill),  whereas  the  actual  force  tending  to  displace  the  model, 
as  shown  by  its  attached  dynamometer,  was  but  .094  of  a  pound  (Col. 
IV) ;  that  is,  the  sum  total  effect  of  the  wind  upon  the  model  is  but 
61  per  cent  (Col.  V)  of  the  calculated  force  based  upon  the  area  of  its 
exposed  or  cross  section.  The  wind  velocity  for  this  experiment  was 
equal  to  36  feet  per  second  (Col.  VI),  or  25  miles  per  hour  (Col.  VII). 

The  last  experiment  recorded  in  the  same  table  shows  the  gauge 
displacement  to  have  been  5  inches  of  water,  which  is  equivalent  to 
a  pressure  of  26  pounds  per  square  foot,  which  pressure,  acting  upon 
an  area  equal  to  the  cross-section  of  the  model,  would  be  expected 
to  result  in  a  force  of  2.52  pounds,  whereas  the  actual  force  tending 
to  displace  the  model,  as  shown  by  its  attached  dynamometer,  was 
but  1.25  pounds  or  49  per  cent  of  the  calculated  force,  based  upon 
the  cross-section  of  the  model.  The  velocity  of  the  current  in  the 
last  experiment  was  102  miles  an  hour. 

A  review  of  all  the  figures  presented  in  this  table  will  show  that, 
in  every  case,  the  force  tending  to  displace  the  model  is  less  than 
that  found  by  multiplying  the  calculated  wind  pressure  of  unit  area 
by  the  area  of  the  cross-section  of  the  model.  The  value  of  the  ratio, 
while  nearly  constant,  tends  to  become  less  as  the  velocities  of  the  air- 
currents  are  increased.  The  error  would  not  be  great  if  the  ratio  of 
the  actual  force  to  the  calculated  force  were  assumed  to  be  always  .5. 

It  is  an  interesting  fact  that  the  direct  pressure  on  the  front  of  the 
model,  the  friction  of  the  wind  along  its  sides  and  top,  and  the  suc- 
tion at  its  rear,  taken  altogether,  should  actually  be  of  less  value  than 
that  which  results  from  the  impinging  stream  of  air  on  the  point  of  the 
gauge,  but  it  is  one  that  is  well  established.* 

*  Two  important  facts  concerning  pressures  resulting  from  air- currents  are:  First, 
that  the  total  pressure  upon  planes  of  different  areas  is  not  necessarily  proportional 
to  the  area  of  the  exposed  surface;  and,  secondly,  that  the  total  pressure  upon  a 
flat  surface  constituting  one  face  of  a  solid  body  is  greatly  affected  by  the  form  cf 


394  LOCOMOTIVE  PERFORMANCE. 

196.  Two  Models. — When  two  models  are  arranged  in  a  train f 
the  first  is  affected  by  the  direct  force  of  the  wind,  while  the  second 
is  affected  by  the  suction  of  the  passing  stream,  and  both  are  influ- 
enced by  the  frictional  effects  of  the  wind  upon  sides  and  top.     The 
results  of  experiments  upon  two  models  are  given  in  Table  LXXXIL, 
in  which,  under  Cols.   IV.    and   V.,  the  effects  upon  the  separate 
models,  and  upon  both  models  taken  together,  are  given. 

In  reviewing  the  first  experiment,  as  presented  in  this  table,  it  will 
be  seen  that,  while  the  calculated  pressure  acting  upon  an  area  equal 
to  that  of  the  cross-section  of  the  train  is  .15  of  a  pound,  the  sum  of  the 
readings  of  the  dynamometer  for  both  models  shows  but  .078  of  a  pound 
or  52  per  cent  of  the  calculated  amount.  This  is  but  a  trifle  more 
than  was  found  for  a  single  model.  An  examination  of  the  table  will 
show  also  that  the  dynamometer  readings  of  the  first  model  were  less 
than  those  observed  when  a  single  model  was  exposed  to  the  influence 
of  the  air-currents  (Table  LXXXI).  This  result  is  due  to  the  fact 
that  the  second  model  removed  from  the  first  the  effect  of  the  suction 
influences.  The  results  show  that  the  force  acting  upon  the  first 
model  was  about  .40  of  the  calculated  force;  that  acting  upon  the 
second  model  about  .14  of  the  calculated  force;  and  that  acting  upon 
the  two  models  together  about  .54  of  the  amount  calculated,  which 
values  are  to  be  compared  with  the  .50  shown  for  one  model.  Doubling 
the  length  of  the  train  resulted  in  this  case  in  an  increase  of  force  in 
the  ratio  approximately  of  .50  and  .54,  that  is,  in  an  increase  of  about 
8  per  cent. 

197.  Trains  of  Three,   Five,   Ten,   and  Twenty-five  Models. — 
The  results  of  experiments  upon  trains,  varying  in  length  from  three 
models    to    twenty-five    models,    appear    in    Tables    LXXXI II.    to 
LXXXVI.  inclusive. 

198.  The  First  Model  of  a  Train. — In  all  of  these  cases  it  will  be 
seen  that  the  forces  acting  upon  the  first  model  are  practically  the 
same  whenever  the  velocity  of  the  current  is  the  same.    The  conclu- 
sion, therefore,  seems  to  be  justifiable  that  whenever  a  train  is  com- 
posed of  more  than  two  models,  the  resistance  of  the  first  model  is 
a  function  of  the  velocity  of  the  air-current  only.     This  statement 
is,  perhaps,  not  absolutely  true,  but  it  is  practically  so.     Again,  the 
value  of  the  force  is,  approximately,  .4  of  the  calculated  force,  based 


the  solid.     Little  has  been  done  as  yet  to  define  exact  relationships  arising  from 
these  conditions. 


ATMOSPHERIC  RESISTANCE   TO  MOTION  OF  TRAINS.     395 

upon  the  pressure  equivalent  of  the  velocity  of  the  wind  as  disclosed 
by  gauge,  and  an  area  equal  to  that  of  the  cross-section  of  the  model. 

199.  The  Last  Model  of  a  Train. — The  forces  to  be  resisted  by 
the  last  model  become  less  as  the  length  of  the  train  i»  increased,  a 
condition  doubtless  due  to  the  fact  that  the  enveloping  layers  of  air 
immediately  about  the  train,  and  which  are   affected   by  frictional 
contact  with  it,  become  thicker  and  thicker  in  passing  from  the  front 
to  the  rear,  with  the  result  that  in  a  long  train  the  currents  immediately 
about  the  last  model  are  less  active  than  when  the  train  is  shorter, 
and  as  a  consequence  the  suction  effect  is  reduced.     The  data  show 
that  with  the  two-model  train  the  rear  model  resists  a  force  which 
is  14  per  cent  of  the  calculated  pressure,  based  upon  the  velocity  of 
the  current  and  the  area  of  the  cross-section  of  the  train;    with  the 
three-model  train  it  is  13  per  cent;  with  the  five-model  train  it  is  12 
per  cent;  with  trains  of  ten  models  in  length  it  is  less  than  10  per  cent; 
but  with  a  train  of  twenty-five  models  it  is  still  about  10  per  cent. 

200.  The  Second  Model  of  a  Train. — In  all  experiments,  when 
more  than  two  models  composed  the  train,  the  forces  acting  upon  the 
second  model  of  a  train  appear  to  have  been  less  than  those  acting 
upon   any   other   model    of    the    train.     This   is   explained   on   the 
assumption  that  the  currents  in  passing  the  first  model  are  so  deflected 
that  some  of  the  wave-like  lines  pass  around  the  second  model,  thus 
relieving  it  of  a  portion  of  the  force  to  which  it  would  otherwise  be 
subjected. 

20 1.  Models  between  the  Second  and  the  Last  of  a  Train.— 
Whatever  the  length  of  the  train,  all  intermediate  models,  the  second 
excepted,  seem  to  have  been  met  by  an  equal  force  regardless  of  their 
location  in  the   train.      Thus,  with  a  ten-model  train  and  a  wind 
velocity  of  64  miles  per  hour,  the  observed  force  in  pounds  acting 
upon  the  several  models  from  the  third  to  the  ninth  inclusive  was  .038, 
.038,  .040,  .038,  .039,  .040,  and  .039  respectively.     For  all  experiments 
the  percentage  of  the  calculated  pressure,  based  upon  wind  velocity 
and  cross-section  of  the  train,  which  appears  as  a  force  acting  upon 
intermediate  cars,  is  shown  to  be  between  3.8  per  cent  and  4  per  cent. 
This,  of  course,  is  the  sum  of  frictional  action  along  sides  and  top, 
and  such  effect  as  may  arise  from  eddies  between  the  models. 

202.  Distribution  of  Forces  Acting  throughout  the  Length  of  the 
Model  Train. — The  preceding  paragraphs  show  that  each  portion  of 
a  train  of  models  presents  a  resistance  to  the  currents  of  air  moving 
past  it,  which  is  a  fixed  percentage  of  the  pressure  equivalent  of  the 


396  LOCOMOTIVE  PERFORMANCE. 

velocity  of  the  current;  or,  to  make  the  statement  more  concise,  the 
resistance  offered  by  each  portion  of  the  train  is  a  constant  function 
of  the  velocity  of  the  current.  This  relationship  is  shown  graphically 
for  a  train  of  ten  models  by  Fig.  224.  It  holds  good  for  all  velocities. 
203.  Relation  of  Force  and  Velocity. — The  relation  between  the 
velocity  of  the  current  and  the  resulting  forces  acting  upon  each 
model  of  a  train  may  be  shown  by  plotting  the  dynamometer  readings 
(Col.  IV)  for  each  of  the  several  models,  with  the  velocities  (Col.  VII) 


Resistance^ 


I 


Cars*    I    i    II    2    II    3    If    4    II    T~ll    G   II    7    II    THi    o    ir~To~l 
FIG.  224. — Relative  Resistance  Offered  by  the  Several  Cars  of  a  Train. 

corresponding.  From  a  smooth  curve  drawn  through  the  points  thus 
obtained,  equations  may  be  written  to  represent  the  velocity,  as 
follows : 

For  a  single  model  alone 

ai  =  .000116F2, (22) 

for  the  first  model  of  a  train 

a/=. 00009772, (23) 

for  the  last  model  of  a  train 

a/=.000025F2, (24) 

for  the  second  model  of  a  train 

a8=.  000008  F2, (25) 

for  any  intermediate  model  of  a  train 

at-=.000010F2 (26) 

In  the  preceding  equations  a  is  force  in  pounds  acting  upon  the 
model  in  the  direction  of  its  length,  and  V  is  velocity  of  the  air-cur- 
rent in  miles  per  hour.  In  the  form  in  which  they  are  given  the 


ATMOSPHERIC  RESISTANCE  TO  MOTION  OF  TRAINS.    397 

equations  are  not  of  general  application,  since  they  are  based  on  the 
dimensions  of  the  particular  models  employed  in  the  experiments. 

Equations  of  a  more  general  character  may,  however,  be  readily 
obtained  by  reducing  the  observed  forces  acting  upon  each  model 
to  equivalent  forces  which  would  have  been  observed  had  the  area 
of  the  cross-section  of  the  models  been  one  square  foot,  the  propor- 
tions of  the  models  remaining  unchanged.  Thus,  the  area  of  the 
cross-section  of  the  actual  models  was  .097  of  a  foot.  By  dividing  the 


11 

a 

I" 


o 

- 


. 

2 


I3 

tn 

!* 


10        20 


40       50       60        70 
Miles  per  Hour 


80 


90      100 
FIG.  225. — Relation  of  Force  and  Velocity. 

observed  dynamometer  readings  by  this  factor,  and  by  plotting  results 
with  corresponding  velocities,  the  curves  shown  in  Fig.  225  are  ob- 
tained. When  P  is  the  pressure  in  pounds  per  square  foot,  and  7 
the  velocity  of  the  air-currents  in  miles  per  hour,  the  following  equa- 
tions representing  the  curves  may  be  written: 
For  the  Pitot  gauge 

P=. 002572, (27) 

for  one  model  alone 

P!=. 001272, (28) 


398  LOCOMOTIVE  PERFORMANCE. 

for  the  first  model  of  a  train 

P/=.001F2, (29) 

for  the  last  model  of  a  train 

Pu=.00026y2, (30) 

for  the  second  model  of  a  train 

P.=  .  00008  72; (31) 

for  any  intermediate  model  between  the  second  and  the  last  of  a 
train 

P;=.000172 (32) 

204.  A  Summary  of  Conclusions  to  be  Drawn  from  the  Work 
with  Models.  When  a  model  having  the  proportions  of  a  standard 
freight-car,  or  when  a  train  of  such  models  is  submerged  in  currents 
of  air,  the  length  of  the  model  or  train  being  extended  in  the  direc- 
tion of  the  current,  effects  are  observed  which,  briefly  stated,  are  as 
follows : 

1.  The  force  with  which  the  current  will  act  upon  each  element 
of  the  train,  or  upon  the  train  as  a  whole,  increases  as  the  square  of 
velocity. 

2.  The  effect  upon  a  single  model,  standing  alone,  measured  in 
terms  of  pressure  per  unit  area  of  cross-section,  is  approximately  .5 
the  pressure  per  unit  area,  as  disclosed  by  the  indications  of  the  Pitot 
gauge. 

3.  The  effect  upon  the  different  models  composing  a  train  varies 
with  different  positions  in  the  train;  it  is  most  pronounced  upon  the 
first  model;    next  in  order  of  magnitude  is  its  effect  upon  the  last 
model;   next,  its  effect  upon  each  intermediate  model  other  than  the 
second ;  and  last  of  all  is  its  effect  upon  the  second  model. 

4.  The  relative  effect  upon  different  portions  of  a  train  is  approxi- 
mately the  same  for  all  velocities.    For  example,  any  intermediate 
model  other  than  the  second  always  has  a  force  to  resist,  which  is, 
approximately,  one-tenth  that  resisted  by  the  first  model,  while  the 
last  model  has  a  force  to  resist  which  is  one-quarter  that  resisted  by 
the  first. 

5.  The  ratio  of  the  effect  upon  each  of  the  several  models  com- 
posing a  train,  measured  in  pressure  per  unit  area  of  cross-section, 
compared  with  the  pressure  per  unit  area  disclosed  by  the  indications 


ATMOSPHERIC  RESISTANCE  TO  MOTION  OF  TRAINS.    399 

•of  the  Pi  tot  gauge,  is,  approximately,  for  the  first  model  of  the  train, 
0.4;  for  the  last  model  of  the  train,  0.1;  for  any  intermediate  model 
between  the  second  and  last,  0.04;  and  for  the  second  model,  0.032. 

205.  Atmospheric  Resistance  to  Actual  Trains. — Thus  far  atten- 
tion has  been  directed  to  the  effects  produced  by  currents  of  air  acting 
upon  fixed  models  similar  to  freight-cars  in  outline  and  proportions, 
but  much  less  in  size.  In  what  measure  the  results  thus  obtained 
will  apply  to  trains  of  actual  cars  moving  through  still  air  is  a  matter 
yet  to  be  considered.  It  is  fair  to  presume  that,  had  the  models  been 
larger  than  those  which  were  really  employed,  the  results  observed 
would  have  been  entirely  consistent  with  those  already  given.  If 
their  dimensions  had  equaled  those  of  a  full-sized  car  even,  there  is 
no  reason  for  supposing  that  the  results  obtained  would  have  been 
disproportional  to  those  which  were  actually  observed  from  the 
.smaller  model,  and  it  may  be  assumed,  therefore,  that  the  effects 
which  would  manifest  themselves  on  a  full-sized  car  of  the  same  pro- 
portions with  the  model  may  be  predicted  with  approximate  accuracy 
from  the  known  effects  produced  upon  the  model. 

A  full-sized  car,  having  the  same  proportions  with  the  models 
used  in  the  experiments,  would  be  a  plain  structure,  33  feet  long  and 
9  feet  wide,  rising  from  a  point  close  to  the  ground  to  a  height  of  12 
feet  along  the  center  and  11  feet  along  the  sides.  When  such  cars 
are  arranged  in  trains  clear  spaces  of  three  feet  would  intervene 
between  them.  This  combination  of  cars  might  be  considered  as 
representing  for  the  present  purpose  an  ideal  train.  The  character- 
istics of  an  actual  train,  however,  are  difficult  to  define.  Cars  vary 
in  the  dimensions  of  their  cross-section,  in  their  length,  and  in  the 
contour  of  their  sides  and  roof.  Box-cars  are  of  simpler  outline  than 
coaches,  and  vestibuled  trains  present  a  more  uniform  cross-section 
than  trains  of  platformed  cars.  Trains  may  be  made  up  of  cars  of 
uniform  size,  or  of  cars  each  one  of  which  may  be  so  different  in  its 
proportions  or  outline  as  to  produce  an  effect  upon  the  atmosphere 
through  which  it  moves  measurably  different  from  that  produced  by 
any  other  car  of  its  train. 

A  careful  review  of  the  subject  will  show  that  differences  in  form 
•or  proportions  existing  between  the  model  and  the  actual  cars  may 
not  be  greater  than  those  existing  between  two  different  types  of 
.-actual  cars.  The  differences  in  effect  arising  from  these  differences 
in  form  and  proportion,  therefore,  may  be  no  greater  in  the  former 
case  than  in  the  latter.  If  this  is  true  the  models  will  serve  as  a  good 


OF  THt 

MM'.VfRSITY 


400  LOCOMOTIVE  PERFORMANCE. 

basis  from  which  to  make  comparisons,  and  the  belief  is  that  the 
results  which  are  given  in  succeeding  paragraphs  are  not  only  suffi- 
ciently accurate  for  every  practical  purpose,  but  that  they  are  as 
nearly  true  as  any  general  statement  applying  to  all  conditions  of 
service  can  be.* 

Before  proceeding  to  a  consideration  of  details,  it  will  be  well  to 
observe  that  estimates  which  have  hitherto  been  calculated  concern- 
ing the  value  of  the  resistance  offered  by  the  atmosphere  to  the  progress 
of  railway  trains  have  been  generally  made  upon  a  tonnage  basis. 
An  explanation  for  this  is  doubtless  to  be  found  in  the  lack  of  knowl- 
edge regarding  atmospheric  action.  As  the  other  resistances  to 
which  a  train  is  subject  are  well  expressed  upon  a  tonnage  basis,  it 
has  been  convenient  to  express  that  which  is  of  uncertain  value  in 
the  terms  of  those  facts  which  are  better  known.  There  is  no  jus- 
tification for  such  a  practice,  for  it  is  obvious  that  the  atmospheric 

*  In  comparing  the  conditions  surrounding  the  model  car  with  those  existing 
about  an  actual  moving  car  several  points  of  difference  are  to  be  noted.  First,  the 
frictional  resistance  offered  by  the  foundations  of  the  model  would  tend  to  reduce 
the  velocity  of  currents  acting  upon  the  lower  portions  of  the  model,  in  which  case 
the  force  acting  upon  the  model  would  be  reduced  below  normal.  Lower  portions 
of  an  actual  car,  however,  are  required  to  pass  through  currents,  which,  because 
of  their  proximity  to  the  ground,  resist  the  motion  of  the  car,  so  that  the  force 
acting  upon  such  portions  of  the  actual  car  are  increased  above  normal.  It  would 
appear,  therefore,  that  results  obtained  from  the  models  would  give  values  which 
are  too  low  when  applied  to  actual  cars.  Such  a  conclusion  is  undoubtedly  justified, 
but  the  differences  in  question  must  be  small,  and  they  are  probably  neutralized 
by  the  fact  that  the  body  of  the  model  car  extends  downward  to  the  foundation, 
completely  filling  the  space  corresponding  to  that  which,  in  the  actual  car,  extends 
between  the  lower  edge  of  the  sills  and  the  surface  of  the  ground,  giving  enlarged 
side  surfaces  and  enlarged  area  of  cross-section. 

Secondly,  the  presence  of  the  foundation  would,  by  frictional  action,  tend  to 
reduce  the  velocity  of  all  portions  of  the  current  in  contact  with  or  close  about 
the  models.  Against  this  tendency  is  to  be  placed  the  fact  that  velocities  were 
determined  at  a  point  where  the  flow  occupied  the  full  cross-section  of  the  con- 
duit. The  presence  of  the  models,  with  their  foundations,  reduced  the  effective 
area  of  the  conduit,  and  necessarily  gave  a  higher  mean  velocity  to  the  current 
while  passing  them.  How  far  the  effects  arising  from  these  two  facts  will  balance 
each  other  cannot  be  told,  but  that  they  are  opposite  is  beyond  question,  and  a 
study  of  conditions  involved  will  show  that  neither  can  be  very  large. 

Thirdly,  the  presence  of  the  sides  of  the  conduit  may  have  served  to  constrain 
the  wave  like  action  set  up  about  the  initial  end  of  the  train,  and  by  so  doing  may 
have  modified  the  effects  observed  for  the  last  and  for  the  intermediate  models. 
Considering  the  relative  cross  section  of  the  conduit  and  the  models  it  is  not 
likely  that  disturbances  arising  from  this  cause  have  led  to  any  considerable  error. 


ATMOSPHERIC  RESISTANCE   TO  MOTION  OF  TRAINS.    401 

resistance  for  a  loaded  car  is  no  greater  than  for  a  light  car,  values 
in  either  case  depending  entirely  upon  the  size,  proportions,  and 
contour  of  the  car.* 

206.  Application  of  Results  Obtained  from  Models.  —  As  the 
models  experimented  with  were  -h  the  size  of  a  typical  full-sized 
car,  which,  for  the  present  purpose,  may  be  assumed  to  represent 
any  33-foot  box-car,  the  area  of  each  surface  presented  in  the  actual 
car  is  (32)2  =  1024  times  the  area  of  similar  surfaces  in  the  model. 
It  is  assumed  that  the  effect  of  the  wind  upon  solids  of  the  same  pro- 
portion will  vary  with  the  extent  of  exposed  surface,  so  that  the 
atmospheric  resistance  which  will  oppose  the  progress  of  the  actual 
car  will  be  to  that  which  would  oppose  the  progress  of  the  model  as 
1024  is  to  1.  That  is,  if  a  is  the  force  in  pounds  resisted  by  the  model 
under  the  conditions  of  the  experiments,  and  A  the  force  due  to 
atmospheric  resistance  to  be  overcome  by  the  actual  car  under  con- 
ditions of  service,  then 

(33) 


Expressions  have  already  been  written  (equations  22  to  26)  giving 
the  force  in  pounds  resisted  by  models  under  the  influence  of  air-cur- 
rents having  a  velocity  of  V  miles  an  hour.  Combining  these  with 
equation  33  gives  the  resistance  in  pounds,  A,  to  be  overcome  by  the 
actual  car  when  moving  in  still  air  at  a  velocity  of  V  miles  an  hour. 

Thus  equation  22,  expressing  the  resistance  offered  by  a  single 
model,  is 

ax  =  .000116y2,        ........     (22) 

and  equation  33  gives 

Ai 

di  =  - 
1024* 

Therefore,  for  a  single  actual  car  alone, 

Ai  =  .00011672X1024, 
or,  approximately, 
__  Ai  =  .119F2  ...........     (34) 

*  There  have  been  numerous  attempts  to  express  the  atmospheric  resistance 
of  a  railroad  train  in  the  form  of  an  equation.  None,  so  far  as  the  writer  is  informed, 
have  taken  into  account  both  the  cross-section  and  the  length  of  the  train,  or  have 
attempted  to  distinguish  between  the  head  resistance  and  the  frictional  resistance 
of  the  intermediate  cars.  In  most  cases,  also,  the  work  has  been  based  upon  an 
assumed  relation  between  pressure  and  velocity  which  has  given  values  greatly 
in  excess  of  those  actually  existing. 


402  LOCOMOTIVE  PERFORMANCE. 

By  a  similar  process  there  may  be  obtained: 
For  the  first  car  of  an  actual  train 

Af  =  .  000097  72X  1024, 
or,  approximately, 

^.09972;       .........     (35) 

for  the  last  car  of  a  train 

A  t  =  .  000025  V2X  1024, 
or,  approximately, 

^  =  .02672;  ..........     (36) 

for  the  second  car  of  a  train 

Aa  =.  000008  X1024F2, 
or,  approximately, 

A«  =  .00872;*  .........     (37) 

for  any  intermediate  car  between  the  second  and  last 

Ai  =  .  000010  X102472, 
or,  approximately, 

A;  =  .010F2  ...........     (38) 

It  is  to  be  observed  that  the  constants  appearing  in  the  five  equa- 
tions immediately  preceding  are  calculated  to  give  directly  the  tractive 
force  in  pounds  necessary  to  move  typical  cars,  which  are  assumed 
to  be  the  equivalent  of  any  actual  freight-cars,  against  the  resistance 
of  the  atmosphere  at  any  rate  of  speed,  V  being  the  rate  of  speed  in 
miles  per  hour. 

The  atmospheric  resistance  for  trains  of  such  cars  is  the  sum  of 
the  resistance  of  the  several  parts.  Thus: 

For  two  cars 


*  This  value  is  so  nearly  equal  to  that  for  Ai,  that,  in  the  work  which  follows, 
the  resistance  of  the  second  car  will  be  assumed  to  be  equal  that  of  any  intermediate 


ATMOSPHERIC  RESISTANCE  TO  MOTION  OF  TRAINS.    403 
for  more  than  two  cars,  calling  the  number  of  intermediate  cars  6,  or 
b=  number  of  cars  in  train  minus  2, 


=  (.125  +  .  0106)  V2', 

or,  since  the  resistance  of  each  intermediate  car  is  a  constant  function 
of  the  velocity,  the  multiplier  in  the  coefficient  of  V  may  readily  be 
expressed  in  terms  of  the  number  of  cars  in  the  train.  Thus,  let 

N  =  number  of  cars  in  train, 
then 

6=^-2, 
and 

A  =  (.125  +  .0106)  V2  =  (.105  +  .OWN)  V2; 

the  last  form  being,  perhaps,  somewhat  more  readily  applied  than 
the  one  preceding. 

In  a  similar  manner,  by  a  suitable  combination  of  equations  34  to 
38,  the  atmospheric  resistance  of  any  train  may  be  expressed. 

207.  Resistance  Offered  to  Locomotive  and  Tender.  —  In  the 
application  of  the  equations  given  in  the  preceding  paragraph,  a 
locomotive  and  tender  running  alone  may  be  regarded  as  two  cars. 
In  a  train  of  freight-cars,  headed  by  a  locomotive  and  tender,  the 
locomotive  should  be  regarded  as  the  first  car  and  the  tender  as  the 
second.  Thus,  the  tractive  force  in  pounds  necessary  to  overcome 
the  atmospheric  resistance  due  to  the  motion  of  a  locomotive  and 
tender  running  alone  is  equivalent  to 


=  .  099  V2+.  026  V2  =  .  125V2, 

which,  for  a  speed  of  40  miles  an  hour,  gives 

•* 

A  =  .125  X  1600  =  200  pounds. 

The  tractive  force  necessary  to  overcome  the  resistance  of  a  looo- 
motive  and  tender  running  at  the  head  of  a  train  is  equivalent  to 


404  LOCOMOTIVE  PERFORMANCE. 

which,  at  a  speed  of  40  miles  an  hour,  gives 
A  =  .109X1600  =  174  pounds. 

208.  Resistance  Offered  to  Trains  of  Freight-cars.  —  A  train  com- 
posed of  a  locomotive,  tender,  and  20  freight-cars,  would,  in  effect, 
be  equal  to  22  freight-car  units.  The  resistance  to  be  overcome 
would  be  that  of  the  first  unit  plus  that  of  20  intermediate  units  plus 
that  of  the  last  unit.  That  is 

6-20, 


*    =.  099  V2+.  010X20  F2+.  026  V2 
=  .325F2, 

which,  at  a  speed  of  40  miles  an  hour,  gives 

A  =  .325X1600  =520  pounds. 

If  it  is  required  to  find  the  force  necessary  to  overcome  the  atmos- 
pheric resistance  of  only  that  portion  of  the  train  which  is  behind 
the  tender,  the  resistance  of  the  first  unit  (in  this  case  the  locomotive) 
and  that  of  the  second  unit  (in  this  case  the  tender)  must  be  removed 
from  the  equation,  that  is,  Af  =  Q  and  6  =  19,  so  that  the  equation 
becomes 


=  .010  X  19F2+  .026  V2  =  .216F2. 

The  resistance,  therefore,  opposing  the  progress  of  the  20  cars  in  a 
train,  following  a  locomotive  and  tender  at  a  speed  of  40  miles  an  hour,  is 

A  =  .216  X  1600  =  346  pounds. 

209.  Resistance  Offered  to  Trains  of  Passenger-cars.  —  The  atmos- 
pheric resistance  of  a  train  of  passenger  coaches  can  be  determined 
by  reducing  .the  number  of  coaches  to  an  equivalent  number  of  freight- 
cars.  In  general,  it  will  be  sufficiently  accurate  if  each  coach  is  made 
equal  to  two  freight-cars.  Thus,  a  train  of  five  coaches  following  a 
locomotive  and  tender  may  be  considered  equivalent  to  12  units,  of 
which  the  locomotive  and  tender  each  count  one.  Numerical  results 
may  then  be  found  as  already  described. 


ATMOSPHERIC  RESISTANCE  TO  MOTION  OF  TRAINS.     405 

210.  Resistance  Offered  to  any  Train  in  Terms  of  its  Length.— 

It  is  evident  that  a  car  length  of  33  feet  as  a  unit  of  measurement 
is  subject  to  some  limitation.  The  equations  already  deduced,  how- 
ever, may  be  transformed  into  equivalent  expressions,  in  which  the 
length  of  the  train  is  expressed  in  feet  rather  than  in  number  of  cars. 
Thus,  considering  the  locomotive  and  tender  as  cars,  the  resistance 
of  the  whole  train  may  be  expressed  in  terms  of  the  resistance  of  an 
intermediate  car.  If  the  actual  number  of  cars  is  N,  and  the  equiv- 
alent number  of  intermediate  cars  D, 

D=  number  of  intermediate  cars  equivalent  to  first 
car  (locomotive)  +  number  of  intermediate  cars  + 
number  of  intermediate  cars  equivalent  to  last  car 

.099      ..     '    '    .026 


.6=N-f  10.5. 

So  that  the  total  resistance  of  any  number  of  cars  composing  a  train, 
when  the  locomotive  and  tender  are  each  regarded  as  a  car,  is  equiva- 
lent to  the  resistance  of  one  intermediate  car  multiplied  by  the  number 
of  cars  plus  10.5.  But  the  resistance  of  an  intermediate  car  is  .OIF2, 
consequently  that  of  the  whole  train  ;s 

^(locomotive  and  train)  =  .  01  (N  +  10.5)  V2,    ....       (39) 

where  A  is  the  number  of  pounds  tractive  force  necessary  to  keep 
the  train  in  motion  against  the  resistance  of  the  atmosphere,  N  the 
number  of  33-foot  cars  in  the  train,  of  which  number  the  locomotive 
and  tender  are  each  counted  one,  and  V  is  the  velocity  in  miles 
an  hour. 

Again,  if  the  length  of  the  train  in  feet  is  represented  by  L,  then 

L=NX33, 
or 


Substituting  this  value  of  N  in  equation  39  gives 

^(locomotive  and  train)  =  -01  (^  +  lO.s)  F2  =  .  0003  (L  +  347)  F2,       (40) 


406  LOCOMOTIVE  PERFORMANCE. 

which  is  the  tractive  force  necessary  to  overcome  the  atmospheric 
resistance  of  the  entire  train  when  the  length  of  the  train  in  feet  is 
known.  Thus,  a  locomotive  and  train  which  measures  800  feet  in 
length  would  be  resisted,  when  running  at  a  speed  of  40  miles  an 
hour,  by  a  force  of 

A  =  .0003(800  +  347)  1600  =  551 . 

By  a  similar  process  the  resistance  of  the  train  following  behind 
a  locomotive  may  be  expressed  as 

A  (excluding  locomotive  and  tender)  =  .0003(/+53)F2,     .     .  (41) 

where  I  is  the  length  in  feet  of  the  train,  excluding  locomotive  and 
tender.  Thus,  if,  in  the  example  just  assumed,  the  locomotive  and 
tender  were  66  feet  long,  the  train  following  the  tender  would  have 
been  800  —  66  =  734.  The  pull  of  the  tender  draw-bar,  when  running 
at  a  speed  of  40  miles  an  hour,  would  be 

A  =  .0003(734+53)  1600  =  378  pounds. 

In  determining  values  for  L  and  I,  in  equations  40  and  41,  the 
length  of  the  car  bodies  only  is  to  be  considered,  since  whatever  resist- 
ance may  arise  because  of  the  space  between  the  cars  is  in  each  case 
included  in  the  value  of  the  constant  appearing  in  the  equation.  It 
is  unnecessary,  also,  to  express  the  length  of  train  with  absolute 
exactness,  since  an  error  of  one  foot  in  the  length  of  the  train  intro- 
duces an  error  of  only  one  pound  in  the  calculated  result  when  the 
speed  is  60  miles  an  hour;  for  a  lower  speed  the  error  in  the  result 
arising  from  errors  in  the  length  of  the  train  is  less  than  this. 

211.  Conclusions. — The  experiments  already  described,  and  the 
results  deduced  therefrom,  justify  certain  conclusions.  These,  while 
stated  in  definite  form,  are  in  fact  subject  to  a  variety  of  conditions 
affecting  their  value,  the  significance  of  which  is  fully  discussed  in 
paragraph  205.  It  will  be  well  to  note  in  this  connection  that  the 
conclusions  here  given  apply  to  trains  and  parts  of  trains  having  an 
area  of  cross-section  equal  to  that  which  is  common  in  American 
practice;  also  that,  being  intended  for  general  use,  they  should  not 
be  expected  to  apply  strictly  in  any  individual  case.  Their  applica- 
tion may,  in  individual  cases,  lead  to  errors  of  from  15  to  20  per  cent, 
but  even  with  this  limitation  the  conclusions  given  are  vastly  superior 
to  any  that  have  hitherto  been  offered;  and,  with  this  limitation  also, 


ATMOSPHERIC  RESISTANCE   TO  MOTION  OF  TRAINS.    407 

they  will  doubtless  be  found  entirely  sufficient  for  every  requirement 
arising  in  practice.     The  conclusions  are  as  follows: 

1.  The  resistance  offered  by  still  air  to  the  progress  of  a  locomo- 
tive and  tender  running  at  the  head  of  a  train  is  approximately  ten 
times  greater  than  that  which  acts  upon  an  intermediate  car  of  the 
same  train. 

2.  The  resistance  offered  by  still  air  to  the  progress  of  the  last  car 
of  a  train  is  approximately  two  and  a  half  times  greater  than  that 
which  acts  upon  an  intermediate  car  of  the  same  train. 

3.  The  resistance  offered  by  still  air  to  the  progress  of  trains  and 
parts  of  trains  may  be  expressed  in  the  form  of  equations,  in  which 
A  is  the  tractive  force  in  pounds  necessary  to  overcome  the  resistance 
of  the  atmosphere,  and  V  is  the  velocity  in  miles  per  hour.     Such 
equations,  in  which  the  values  of  constants  are  given  to  two  signifi- 
cant figures,  are  as  follows: 

(a)  For  a  locomotive  and  tender  running  alone 


(b)  For  a  locomotive  and  tender  running  at  the  head  of  a  train 

A  =  .nv2. 

(c)  For  the  last  car  of  a  train  of  freight-cars 


(d)  For  the  last  car  of  a  train  of  passenger-cars 

A  =  .036  72. 

(e)  For  each  intermediate  freight-car  in  a  train  of  33-foot  cars 


(/)   For  each  intermediate  passenger-car  in  a  train  of  66-foot  cars 

A  =  .0272. 
(g)  For  a  train  consisting  of  locomotive,  tender,  and  freight-cars 


where  C  is  the  number  of  cars  in  the  train. 

(h)  For  a  train  consisting  of  locomotive,  tender,  and  passenger- 
cars 


where  C  is  the  number  of  cars  in  the  train. 


408 


LOCOMOTIVE  PERFORMANCE. 


(i)   For  a  train  of  freight-cars   following  a  locomotive,  but  not 
including  either  locomotive  or  tender, 

A  =  (.016  +  .  01(7)  F2, 

where  C  is  the  number  of  cars  in  the  train. 

(/)    For  a  train  of  passenger-cars  following  a  locomotive,  but  not 
including  either  locomotive  or  tender, 


.02C)F2, 


where  C  is  the  number  of  cars  in  the  train. 

(k)  For  a  locomotive  and  any  train,  either  freight  or  passenger, 


where  L  is  the  length  of  the  train  in  feet. 

(Q    For  a  train  of  cars,  either  passenger  or  freight,  following  a 
locomotive,  but  not  including  either  locomotive  or  tender, 

A  =  .0003(1+  53)  V2, 

where  I  is  the  combined  length  of  the  cars  composing  the  train. 

4.  A  partial  summary  of  results  in  convenient  form  is  presented 
as  Tables  LXXXVIL,  LXXXVIIL,  and  LXXXIX. 


TABLE  LXXXVIL 

RESISTANCE  OFFERED  BY  STILL  AIR  TO  THE    PROGRESS    OF  A 
LOCOMOTIVE  AND  TENDER. 


Locomotive  and  Tender 

Locomotive  and  Tender  Running  at 

Speed  in  Miles 

Running  Alone. 

the  Head  of  a  Train. 

per  xlour* 

.Tractive  Force. 

Horse-power. 

Tractive  Force. 

Horse-power. 

10 

13 

0.35 

11 

0.29 

20 

52 

2.8 

44 

2.3 

30 

117 

9.4 

99 

7.9 

40 

208 

22 

176 

19 

50 

325 

43 

275 

37 

60 

468 

75 

396 

63 

70 

637 

119 

539 

101 

80 

822 

178 

704 

150 

90 

1050 

253 

891 

214 

100 

1300 

347 

1100 

293 

3  §1 


ATMOSPHERIC  RESISTANCE  TO  MOTION  OF   TRAINS.    409 

i-H  IO          O>  CO 

-H        CM 


B 
J 

W 

t3 


W  a 


?Oi—  <O 
T^Ot^ 
CO  OS  CO 


OOO 
i—  i  o  Tt* 
iOt'-O 


i—  i        (N        CO 


OOOOO 

r—  I  ?O  00  OS  I> 

O^OiiOCM 

»-H  I—  1  l-H  (N  CO 


S 


Or-ioosiooo^ocsoo 

^H          i—  1          CO          "*          CO          O 


»-H     O, 


»O 


WE, 


CO         00 
O^COOOCOOS 


J.      o5 

2>§  I 

EH      h    | 


^        OS 
iO 


II 


i^e  I  2    ?2    i3    S 

!'"(2  I  ^     M 


O 
iO 


I    CO 
|g       I    CO         OS         1> 

a  i  °  N  °  8 


(M        OO        CO 


i—  (lOlOCOt^- 


410 


LOCOMOTIVE  PERFORMANCE. 


e«  8 

J--J 


o  o  o 

T*  05  CO 

OS  O5  i— < 

CO  •*  CO 


I 


i— I        «5        (M 

co      1-1      "* 
^      co      ce 


• 


II 


o  o 

T»(  r- 

CO  O 

i-H  (N 


oo       co       co 
r-      t»      i— i 

i— I         CO 


(N        l>        O        05 

<M  i-H  Tj<  00 

•-I       c^       co       T* 


o      o 

!>•         O 

GO          i— I 


I    GO 

• 

I  o 


(M        »O        C5        IO        i— i 

^          O5          CO          CO          OO 
<~H         C^l          CO 


33    S-< 

II 


O          CO          1-4 

co      co      cq 


CO  U5 
00  p- 1 
"<*  CO 


in     I  2 

JIM 


i  s 


CHAPTER  XXIV. 
A  GENERALIZATION  CONCERNING  LOCOMOTIVE    PERFORMANCE. 

212.  Application  of  Data. — From  the   data  derived  from  Sehe- 
nectady  No.  1  it  is  possible  to  make  estimates  concerning  the  per- 
formance  of   locomotives   in   general,    and    to    construct   equations 
expressing  performance  with  reference  to  several  important  functions. 

213.  Boiler  Performance. — Dealing  first  with  the  matter  of  evap- 
orative power,  the  following  facts  are  to  be  noted :  The  records  obtained 
from  the  Purdue  locomotive  disclose  several  tests  for  which  the  evap- 
oration is  above  12  pounds  of  water  per  foot  of  heating-surface  per 
hour,  and  the  maximum  record  for  the  boiler  is  14.6.     The  results 
were  obtained  with  Brazil  block  coal,  which  is  of  a  light  and  rather 
friable  character.     While  they  were  secured  at  the  expense  of  very 
hard  firing,  it  is  probable  that,  with  a  superior  grade  of  fuel,  higher 
rates  of  evaporation  could  have  been  had,  and  that  a  possible  maxi- 
mum for  this  boiler  need  not  be  lower  than  15  pounds.     In  accepting 
this  limit  it  should  be  considered  a  possible  maximum  merely.      It 
is  at  least  three  pounds  higher  than  the  practical  maximum  which 
<?an  be  relied  upon  in  service  for  continuous  work  using  Brazil  coal. 
For  short  intervals  of  time  the  output  of  a  locomotive  boiler  may 
l>e  greatly  increased  beyond  the  normal  maximum,  but  this  is  done 
at  the  sacrifice  of  fire  condition  or  of  water  level.     Power  obtained 
l>y  such  means  is  the  result  of  abnormal  development,  and  is  not  a 
subject  for  consideration  in  connection  with  the  present  discussion. 

From  these  considerations  it  is  proposed  to  accept  12  pounds  of 
water  per  foot  of  heating-surface  per  hour,  as  a  fair  measure  of  high 
performance  for  the  Purdue  locomotive  under  the  ordinary  conditions  of 
the  road,  and  as  a  close  approach  to  the  maximum  evaporative  power 
of  all  locomotives.  With  this  understanding  the  value,  12  pounds 
of  water  per  foot  of  heating-surface,  will  be  accepted  as  a  measure,  by 
use  of  which  the  power  of  any  locomotive  may  be  predicted.  It  is 

411 


412  LOCOMOTIVE  PERFORMANCE, 

certainly  one  which  can  be  accepted  for  all  boilers  of  similar  design. 
Probably,  also,  it  will  apply  to  all  ordinary  boilers  in  locomotive 
service,  though  this  is  not  settled  beyond  doubt.  It  has  been  suggested 
that  boilers  having  large  grates  may  be  easily  forced  to  higher  limits 
than  those  given,  while  boilers  having  a  large  extent  of  heating-sur- 
face and  small  grates  may  have  difficulty  in  working  up  to  the  limit 
of  12  pounds.  This  argument  is  not  without  force,  though  probably 
it  has  less  significance  than  would  at  first  appear.  Grate  areas  have 
an  important  influence  on  the  efficiency  of  a  boiler,  but  it  is  not  clear 
that  they  can  operate  greatly  to  increase  the  power.  If,  in  each  of 
two  boilers,  one  having  a  wide  grate  and  the  other  a  narrow  grate, 
the  same  amount  of  heat  is  liberated,  the  heat  in  passing  the  tubes 
should  in  each  case  produce  the  same  evaporation.  On  the  other 
hand,  the  advantage  of  the  large  grate  as  a  power  producer  appears 
in  its  ability  to  withstand  forcing,  and  it  must  be  admitted  that  an 
effort  to  secure  maximum  power  in  a  locomotive  is  likely  to  resolve 
itself  into  a  fuel-burning  contest.  In  such  a  contest  the  larger  grate 
is  likely  to  have  some  advantage,  but,  for  reasons  stated,  differences 
on  this  account  will  not  be  great. 

On  the  other  hand,  very  large  locomotives,  if  hand-fired  by  a 
single  man,  can  be  made  to  work  up  to  this  limit  of  12  pounds 
of  water  per  foot  of  heating-surface  per  hour  only  with  great  diffi- 
culty and  usually  for  intervals  of  time  which  are  brief.  In  this 
case  the  limit  upon  the  output  of  power  is  found  not  in  the  propor- 
tions of  the  locomotive,  but  in  the  strength  and  endurance  of  the 
fireman.  The  capacity  of  the  locomotive  is  present,  and  may  be 
utilized  whenever  means  are  found  for  feeding  it.  This  inherent 
capacity  is  the  factor  for  which  a  value  is  sought. 

Finally,  it  should  be  said  that  the  measure  proposed  cannot  be 
a  precise  one.  It  is  based  on  actual  evaporation,  which  is  necessarily 
influenced  by  changes  in  steam  pressure  and  in  temperature  of  feed, 
but  it  is  evident  that  the  requirements  of  the  present  process  are  not 
such  as  to  make  it  necessary  to  take  these  into  account. 

From  these  considerations  it  will  appear  that  the  measure  pro- 
posed is  not  likely  .to  pass  unchallenged;  but,  as  one  studies  the 
problem,  he  will  gain  confidence  in  its  value.  For  the  present  pur- 
pose, therefore,  it  will  be  assumed  that  the  performance  of  all  boilers 
may  be  predicted  from  the  known  extent  of  their  heating-surface; 
that  the  measure  proposed  is  not  a  measure  of  maximum  perform- 
ance, but  is  a  close  approximation  thereto;  and  that  the  measure 


GENERALIZATION.  413 

is  a  fairly  representative  maximum  for  ordinary  conditions  of  service. 
The  measure  expressed  in  the  form  of  an  equation  is 

Water  evaporated  per  hour  =  12  (feet  of  heating-surface  in  boiler),  or 

E  =  12H. 

For  example,  a  modern  passenger  locomotive  having  3500  feet  of 
heating-surface  should,  when  working  continuously  at  its  maximum 
power,  deliver  per  hour 

#  =  12X3500  =  42,000  pounds  of  steam. 

214.  Cylinder  Performance. — Having  now  a  measure  of  the 
weight  of  steam  which  a  locomotive  boiler  may  be  depended  upon 
to  deliver,  we  may  next  make  inquiry  concerning  the  degree  of  economy 
attending  the  consumption  of  steam  by  the  cylinders.  The  steam 
consumption  per  horse-power  for  the  Purdue  engine,  for  all  speeds 
and  cut-offs  within  its  range  of  action,  under  a  full  throttle,  has 
already  been  presented  (Fig.  66,  Chapter  V).  Assuming  that  this 
engine  was  designed  to  work  at  speeds  varying  from  25  to  55  miles 
an  hour,  and  at  loads  necessitating  a  cut-off  of  from  6  to  10  inches, 
there  are  required  from  26.28  to  32  pounds  of  steam  per  horse- 
power per  hour.  The  maximum  limit  of  32  pounds  is  exceptional. 
A  single  value  which  fairly  represents  the  actual  performance  of  this 
17X  24  engine,  working  under  130  pounds  steam  pressure,  is  28  pounds, 
and  this  value  will  for  the  present  be  accepted  as  representing  the 
normal  performance  of  a  modern  engine  under  its  usual  range  of 
action.  It  is  not  the  minimum  value,  for  this  is  from  2  to  3£  pounds 
lower;  nor  is  it  the  maximum,  for  the  maximum  may  greatly  exceed 
the  measure  stated.  But  it  is,  as  has  been  stated,  a  value  which 
represents  the  average  consumption  under  such  range  of  action  as 
is  normal  to  ordinary  service. 

We  are  now  prepared  to  express  cylinder  power  in  terms  of  heat- 
ing-surface. Thus,  if  28  pounds  of  steam  are  required  each  hour  for 
the  development  of  a  horse-power,  and  if  each  foot  of  heating-surface 
yields  12  pounds  of  steam  per  hour,  then  as  many  feet  of  heating- 
surface  will  be  required  for  one  horse-power  as  28  will  contain  12, 
or  2J.  That  is, 

«  , .    ,    • ,  total  pounds  of  water  evaporated  per  hour 

Cylinder  horse-power  =  — 

pounds  consumed  per  horse-power  per  hour 

_  12  X  square  feet  of  heating-surface  in  boiler 

~~w 

=  0.43  (square  feet  of  heating-surface). 


414  LOCOMOTIVE  PERFORMANCE. 

Or,  calling  the  cylinder  power  C.H.P.,  and  the  square  feet  of  heating- 
surface  in  the  boiler  H }  we  have 

C.H.P.  =0.43# (42) 

For  example,  the  maximum  cylinder  power  under  continuous 
conditions  of  operation  of  a  modern  passenger  locomotive  having 
3500  feet  of  heating-surface  is 

C.H.P.  =  0.43  X  3500  =  1500  (approximately) . 

As  this  equation  is  one  of  great  significance,  it  should  be  noted 
that  the  process  leading  up  to  its  development  has  presented  several 
steps,  some  of  which  have  been  subject  to  qualification.  It  is  evident 
that  the  accuracy  of  the  concluding  statement  cannot  be  greater 
than  that  of  the  parts  of  which  it  is  composed.  It  does  not  apply 
With  strict  accuracy  to  any  particular  engine,  or  to  any  specific  con- 
dition of  running.  It  is  merely  an  approximate  measure  of  the  maxi- 
mum power  which  will  be  developed  by  a  fairly  representative  modern 
engine  under  ordinary  conditions  of  service.  Its  use  is  justifiable 
because  of  certain  interesting  and  useful  comparisons  which  it  permits. 

215.  Draw-bar  Pull. — When  the  horse-power  and  speed  of  a 
locomotive  are  known  its  draw-bar  stress  may  be  easily  calculated, 
assuming  no  loss  in  transmission  from  the  cylinder  to  the  draw-bar. 
Thus,  for  any  locomotive, 

Work  developed   in  the  cylinders  =  the  work  given  out  at  the  draw- 
bar. 
Therefore, 

Cylinder  horse-power  X  33,000X60  =  pounds  stress  in*  draw-bar  X  dis- 
tance passed  over  in  feet  in  one 
hour 
= stress  in  draw-bar  X  speed  of  train 

in  miles  per  hourX  5280. 
Transposing, 

horse-power  X  33, 000  X  60 


Pounds  draw-bar  stress  = 


speed  of  train  in  miles  per  hour  X  5280' 


This  is  a  general  expression,  true  of  any  locomotive.     Now,  the 
horse-power  of  the  typical  engine  has  been  shown  to  be  C.H.P.  = 


GENERALIZA  TION.  415 

0.43  X  feet  of  heating-surface,  and  substituting  this  value  for  horse- 
power in  the  preceding  equation. 

0.43X  33, 000 X  60 X  feet  of  heating-surface 

rounds  draw-bar  stress  =  — rrr r- — : — : n -, 

528UX  speed  oi  tram  in  miles  per  hour 

cylinder  horse-power 
speed  in  miles  per  hour 

=  375^.  (43) 


This  equation  is  assumed  to  be  of  general  application.  Applying 
it  to  the  modern  passenger  locomotive  employed  in  the  previous 
illustration,  having  3500  feet  of  heating-surface  and  developing  1500 
horse-power,  it  appears  that  for  a  speed  of  10  miles  an  hour  such  a 
locomotive  will  exert  at  the  draw-bar  a  pull  of 

56,250  pounds, 
and  at  a  speed  of  50  miles  an  hour  but 


=  11,250  pounds. 
o(J 

The  draw-bar  pull  for  all  speeds  for  such  a  locomotive  is  given  by 
Fig.  226.  This  diagram,  applying  only  to  an  engine  of  the  dimensions 
stated,  represents  its  maximum  tractive  effort,  assuming  that  all 
the  energy  of  the  cylinders  appears  as  a  stress  on  the  draw-bar.  So 
far  as  the  mathematical  relations  involved  are  concerned,  the  curve 
may  be  extended  in  either  direction  indefinitely,  but  practical  con- 
siderations establish  limits.  The  limit  of  its  extent  upward  is  found 
when  the  tractive  force  equals  the  adhesion  of  the  locomotive,  and 
the  limit  of  its  extent  to  the  right  is  reached  when  the  speed  of  revo- 
lution reaches  a  fixed  maximum.  Assuming  the  weight  on  drivers 
to  be  96,000  pounds,  and  the  adhesion  to  be  one-fourth  this  amount, 
the  maximum  pull  which  the  drivers  will  transmit  is  23,750  pounds; 
that  is,  on  the  line  AB,  Fig.  226.  The  maximum  speed  is  somewhat 
more  difficult  to  fix.  Assuming  that  the  locomotive  has  79-inch 
drivers,  and  that  they  may  be  allowed  to  travel  as  many  miles  per 
hour  as  they  are  inches  in  diameter,  the  limit  of  speed  will  obviously 
be  79  miles,  cutting  off  the  diagram  along  the  line  CD,  Fig.  226. 


416 


LOCOMOTIVE  PERFORMANCE. 


Within  limits  thus  defined  the  curve  is  a  perfect  definition  of  the 
theoretical  maximum  pulling-power  of  the  engine  under  consideration. 
It  shows  that  the  engine  may  be  started  from  rest  at  its  maximum 
tractive  force  of  23,750  pounds,  and  may  continue  to  exert  this  force 
until  a  speed  of  24  miles  an  hour  is  reached.  At  this  speed  (point  B) 
the  power,  which  at  lower  speeds  has  been  less  than  that  which  the 


Speed  in  Miles  per  Hour. 
FIG.  226. — Draw-bar  Pull  as  Affected  by  Speed. 

cylinders  are  capable  of  exerting,  becomes  maximum  at  1500  horse. 
Beyond  this  point  each  increment  of  speed  is  attended  by  a  loss  in 
tractive  force,  until  at  the  maximum  speed  of  79  miles  it  becomes 
reduced  to  7000  pounds.  It  is  worthy  of  especial  note  that  the  reduc- 
tion in  draw-bar  stress  with  increased  speed  is  not  due  to  any  reduc- 
tion in  the  power  of  the  engine,  but  is  in  response  to  a  physical  con- 
dition which  must  always  prevail;  namely,  that,  when  the  available 
power  is  constant,  the  force  in  action  must  diminish  as  the  velocity 
increases.* 

*  The  proportions  chosen  for  purpose  of  illustration  in  this  and  the  preceding 
examples  are  those  of  a  New  York  Central  Atlantic  type  passenger  locomotive. 


GENERALIZA  TION.  417 

216.  Losses  between  Cylinder  and  Draw-bar. — Thus  far  in  the 
discussion  it  has  been  assumed  that  no  loss  occurs  in  transmitting 
the  power  of  the  cylinder  to  the  draw-bar.  As  a  matter  of  fact, 
losses  occur  which  are  due  to  the  following  causes : 

I.  Machine  friction  of  the  engine,  including  the  rolling  resistance 
of  drivers. 

II.  Rolling  resistance  of  trucks  and  tender. 

III.  Resistance  which  the  atmosphere  offers  to  the  head  of  the 
train. 

There  may  be  other  resistances  as,  for  example,  the  flange  friction 
due  to  side-winds,  which  may  result  in  loss  of  power,  but  these  are 
exceptional  and  are  constantly  varying  in  value.  For  this  reason 
they  have  no  place  in  a  consideration  of  the  general  case  with  which 
we  are  now  concerned. 

A  general  equation  for  machine  friction  may  be  written  either 
in  terms  of  mean  effective  pressure  or  of  draw-bar  stress.  In  anticipa- 
tion of  such  an  equation  we  may  write 

Z)  =  Diameter  of  drivers,  feet; 
d=       "  "  cylinders,  inches; 

L  =  Length  of  stroke,  feet; 
N  =  Number  of  strokes  in  one  revolution; 
P  =  Mean  effective  pressure; 
t  =  Draw-bar  stress. 


Remembering,  also,  that  with  no  loss  in  transmission, 

The  foot-pounds  of  work  1  f  The  foot-pounds  of  work 
given  out  at  the  draw-bar  [  =  -j  developed  in  the  cylin- 
in  one  revolution  J  I  der  in  one  revolution, 

it  is  evident  that 


•'*!?• 

4 
or 


which  will  give  the  draw-bar  stress  whenever  the  mean  effective 
pressure  and  the  necessary  dimensions  of  the  locomotive  are  known. 
If,  therefore,  the  value  of  P  be  made  that  which  is  just  sufficient  to 
keep  the  engine  in  motion  against  its  own  friction,  its  corresponding 


418  LOCOMOTIVE  PERFORMANCE. 

value  will  be  draw-bar  stress  equivalent  to  the  machine  friction. 
From  conclusions  elsewhere  presented  (Chapter  XIX)  it  appears  that 
for  the  Purdue  locomotive  Schenectady  No.  1,  the  frictional  resistance 
may  be  represented  by  a  mean  effective  pressure  of  3.8  pounds, 
and  that  this  value  remains  fairly  constant  for  all  speeds  and  cut-offs. 
Whether  the  higher  pressures  of  the  more  modern  engine  operate  to 
increase  this  value  cannot  definitely  be  determined,  but  the  indica- 
tion is  that  the  increase,  if  any,  would  be  slight.  In  the  absence  of 
more  definite  information,  we  can  do  no  better  than  to  accept  the  value 
stated  as  of  general  application.  If,  therefore,  the  value  3.8  be  sub- 
stituted for  P  in  the  preceding  equation,  and  if  it  is  remembered  that 
for  simple  locomotives  N  equals  4,  the  frictional  resistance  in  pounds 
stress  at  the  draw-bar  may  be  written 


(44) 


which  as  an  approximate  measure  may  be  accepted  as  true  of  any 
simple  locomotive. 

For  the  Purdue  locomotive  the  machine  friction  is 

tl  =  3'8  TIT  =  418  P°unds> 

while  for  a  modern  Atlantic  type  passenger-engine,  previously  employed 
as  an  illustration,  having  cylinders  21"  by  26"  and  drivers  79", 

441  V  2  1  fi 

ti  =  3.8       ;V      -  548  pounds. 
o.b 

This  force  must  be  exerted  at  the  draw-bar  to  keep  in  motion 
the  pistons,  cross-heads,  valves,  rods,  and  all  connected  machine 
parts,  including  the  axles  and  flanges  of  coupled  wheels.  The  sig- 
nificance of  this  statement  is  shown  by  the  line  CD  (Fig.  227).  It  is 
independent  of  speed. 

The  resistance  to  rolling,  offered  by  trucks  and  tender,  cannot 
be  much  different  from  that  of  an  equal  weight  of  train  following  the 
tender.  This  is  often  expressed  by  the  formula 

f  =  2  +  1/67,  ........     (45) 

in  which  t  is  the  resistance  of  each  ton  weight,  and  V  is  the  velocity 
in  miles  per  hour.     This  equation  may  be  accepted  as  of  general 


GENERALIZATION. 


419 


application.  To  apply  it  the  value  of  the  rolling  load  must  be  known. 
The  rolling  load  for  the  modern  passenger-engine,  hitherto  employed 
as  an  illustration,  exclusive  of  that  carried  by  drivers,  the  resistance 
of  which  has  been  included  with  the  machine  friction,  is  as  follows: 

Weight  on  truck 42,000 

"      "  trailing  wheel 48,300 

' '      "  tender  in  working  order 110,900 

Total..  .  201,200 


2^000 


*2 


1-,000 


NX 


550 


riction 


Speed  (S)  in  Miles  per  Hour 
FIG.  227. — Losses  between  Cylinders  and  Draw-bar. 

The  formula  shows  that  the  tractive  force  necessary  to  overcome 
this  rolling  load  of  practically  100  tons,  at  a  speed  of  ten  miles  an 
hour,  is  366  pounds,  and,  for  a  speed  of  50  miles  an  hour,  1033  pounds, 
values  for  all  speeds  being  shown  by  the  line  EF,  Fig.  227. 

Experiments  to  determine  the  resistance  offered  by  the  atmos- 
phere to  the  head  of  a  train  (Chapter  XXIII)  show  that  the  progress 
of  the  locomotive  and  tender  is  resisted  by  a  force  approximately 


420  LOCOMOTIVE  PERFORMANCE. 

ten  times  greater  than  that  which  acts  upon  an  intermediate  car  of 
the  same  train,  the  formula  being 


(46) 


where  t%  is  the  tractive  force  in  pounds  necessary  to  overcome  the 
resistance  offered  by  still  air  to  the  progress  of  a  locomotive  at  the 
head  of  a  train,  and  V  the  velocity  of  the  train  in  miles  per  hour.  The 
formula  makes  the  resistance  which  the  atmosphere  offers  to  the 
motion  of  a  locomotive,  at  a  speed  of  10  miles  an  hour,  11  pounds; 
and  at  a  speed  of  50  miles,  275  pounds,  and  for  all  speeds  as  shown 
by  the  curve  GH,  Fig.  227. 

We  have  now  obtained  a  general  measure  of  the  draw-bar  stress 
equivalent  to  the  power  developed  in  the  engine  cylinders,  assuming 
no  loss  in  transmission,  and  have  applied  the  same  to  modern  pas- 
senger locomotives  (Fig.  226);  also  values  for  the  several  losses  which 
in  service  occur  between  the  cylinder  and  the  draw-bar  (Fig.  227). 
If,  now,  we  apply  these  latter  measures  as  corrections  to  the  former, 
the  results  should  be  a  measure  of  the  forces  actually  developed  at 
the  draw-bar.  The  effect  of  this  process,  as  applied  to  the  modern 
locomotive,  is  most  easily  made  apparent  by  a  graphical  process,  in 
which  the  curves  of  Fig.  227  are  combined  with  that  of  Fig.  226. 
The  result  is  shown  by  Fig.  228.  In  this  figure  the  curve  AB  is  the 
same  as  that  given  in  Fig.  226.  It  is  the  draw-bar  pull  as  calculated 
from  cylinder  work,  disregarding  engine  friction  and  all  other  inci- 
dental losses.  Applying  to  this  curve  the  correction  for  machine 
friction  which  is  denned  by  the  curve  CD,  Fig.  227,  we  shall  need 
to  measure  down  on  each  ordinate  a  distance  from  the  curve  AB 
of  550  pounds.  The  result  is  the  line  CD,  Fig.  228.  Similarly,  to 
make  a  further  correction  for  the  resistance  of  the  rolling  load,  values 
from  the  curve  EF,  Fig.  227,  are  laid  off  downward  from  the  curve 
CD,  resulting  in  the  line  EF,  Fig.  228.  And,  finally,  to  correct  for 
wind  resistance,  values  from  the  curve  GH,  Fig.  227,  are  laid  off 
downward  from  the  curve  EF,  resulting  in  the  curve  GH,  Fig.  228. 
In  the  completed  diagram  the  area  between  the  first  curve  AB  and 
the  second  CD  represents  frictional  losses;  that  between  the  second 
CD  e,nd  third  EF  the  rolling  resistance  of  trucks  and  tenders  ;  that 
between  the  third  EF  and  the  fourth  GH  atmospheric  resist- 
ance; and  that  between  the  fourth  GH  and  the  horizontal  axes 
the  forces  which  are  available  at  the  tender  coupler  for  useful  work 
in  drawing  a  train.  It  will  be  seen  that,  at  a  speed  of  25  miles  an 


GENERALIZA  TION. 


421 


hour,  the  stress  at  the  draw-bar  is  21,500  pounds;  while,  when  the 
speed  is  increased  to  75  miles  an  hour,  the  draw-bar  stress  is  reduced 
to  5000  pounds. 

Some  insight  as  to  the  effect  of  proportions  upon  performance  at 
speed  may  be  had  by  comparing  the  percentage  of  the  cylinder  effort, 
which  is  lost  when  the  speed  is  low,  with  that  which  is  lost  when  the 
speed  is  high.  Thus,  at  a  speed  of  25  miles  an  hour,  the  line  UV 


25;000 


20:000 


15;000 


10,000 


-5400 


20 


40 


GO 


Y      80 


I  100 


I'JO 


Speed  in  Miles  per-Hour. 
FIG.  228.— A  Characteristic  Diagram  of  Locomotive  Performance. 

is  only  7.5  per  cent  of  the  line  UX,  while  at  a  speed  of  75  miles  an 
hour  the  line  ZW  is  40  per  cent  of  the  line  ZY.  '  The  relation  of 
lost  work  to  total  work  developed  in  the  two  cases  is  proportional  to 
the  length  of  the  lines  referred  to. 

217.  The  Application  of  Results  to  several  Typical  Locomotives. — 
The  values  shown  by  Figs.  227  and  228  are  applicable  to  the  New 
York  Central  Atlantic  type  passenger-engine  only,  but  similar  rela- 
tionships may  readily  be  developed  which  will  be  of  general  applica- 
tion. The  general  case  can  best  be  developed  by  means  of  the  equa- 
tions of  the  several  curves  involved,  which  are  given  together  in 


422 


LOCOMOTIVE  PERFORMANCE. 


paragraph  218.     The  result  of  their  application  to  four  well-known 
engines  is  shown  by  Fig.  229. 

A  study  of  the  diagrams  of  Fig.  229  will  disclose  some  of  the  advan- 
tages which  attend  the  use  of  heavy  and  powerful  engines.    Thus, 


10  20  30  40  50    60  70  80  90  100 


FIG.  229. — Characteristic  Diagrams  of  Several  Typical  Locomotives. 

comparing  the  performance  of  the  Purdue  locomotive,  a  representative 
engine  of  the  year  1895,  with  that  of  the  modern  New  York  Central 
Atlantic  type,  it  appears  that,  at  a  speed  of  60  miles  an  hour,  the 
actual  draw-bar  stress  of  the  former  is  reduced  to  below  2000  pounds, 
while  that  of  the  latter  is  not  less  than  7000  pounds.  At  70  miles 
an  hour  the  pull  of  the  Purdue  engine  drops  to  a  thousand  pounds, 


GENERAL1ZA  TION.  423 

whereas  that  of  the  New  York  Central  engine  is  five  times  this  amount. 
These  are  results  due  to  the  greater  power  available,  and  to  the  fact 
that  the  losses  between  cylinder  and  draw-bar  are  relatively  less  for 
heavier  engines  than  for  lighter  ones. 

Some  of  the  effects  of  different  diameters  of  drivers  are  to  be  seen 
by  a  comparison  of  the  diagrams  of  the  Pittsburgh,  Bessemer  &  Lake 
Erie  engine  and  the  Lake  Shore  &  Michigan  Southern  engine.  The 
former,  with  its  54-inch  drivers  and  its  enormous  adhesive  weight, 
gives  at  slow  speed  a  draw-bar  pull  of  not  less  than  55,000  pounds, 
which  is  more  than  50  per  cent  in  excess  of  the  maximum  pull  of  the 
Lake  Shore  engine.  The  small-wheeled  engine  is  able  to  develop 
the  full  power  of  its  cylinders  when  a  speed  of  10  miles  an  hour  is 
reached,  whereas  this  result  is  not  secured  by  the  large-wheeled  engine 
until  a  speed  of  18  miles  an  hour  is  attained.  Correcting  for  losses 
between  the  cylinder  and  draw-bar,  it  appears  that,  for  a  speed  of 
40  miles  an  hour,  the  tractive  effort  of  the  two  engines  becomes  equal. 
Again,  assuming  the  maximum  speed  in  miles  per  hour  to  equal  the- 
diameter  of  the  drivers  in  inches,  the  Pittsburgh,  Bessemer  &  Lake 
Erie  engine  reaches  its  limit  at  54  miles,  whereas  the  Lake  Shore 
engine  continues  to  run  until  80  miles  are  reached.  Actual  difference 
in  respect  to  maximum  speed  would  be  greater  than  that  which  is 
shown;  for,  while  the  Lake  Shore  engine,  with  its  large  wheels  and 
proportionately  lighter  reciprocating  parts,  may  readily  attain  a  speed 
approaching  400  revolutions,  such  a  speed  would  be  impossible  with 
the  smaller  wheels  and  proportionally  heavier  reciprocating  parts  of 
the  Pittsburgh,  Bessemer  &  Lake  Erie  engine.  The  basis  of  com- 
parison in  this  respect  is,  therefore,  more  favorable  to  the  small- 
wheeled  engine  than  it  should  be.  If  the  maximum  speed  limit  of  the 
small-wheeled  engine  be  fixed  at  40  miles  an  hour,  its  entire  range 
of  action  is  represented  by  the  area  of  the  diagram  to  the  left  of  the 
40-mile  line,  which  area  is  to  be  compared  with  the  full  area  of  the 
diagram  of  the  large-wheeled  engine.  It  will  be  seen  that  increasing 
the  diameter  of  the  drivers  greatly  increases  the  possible  range  of 
action,  and,  further,  as  it  tends  to  diminish  fnctional  losses,  it  serves 
in  sustaining  the  draw-bar  pull  as  the  speed  is  increased. 

218.  A  Summary  of  Results,  expressed  in  the  form  of  general 
equations  applicable  to  any  locomotive,  is  as  follows: 

Draw-bar  stress  based  on  cylinder  performance, 

I.H.P.=C.H.P.=0.43#,      .     .     ,  (42) 


424  LOCOMOTIVE  PERFORMANCE. 

.........     (43) 

161^  ........     (47) 

Corrections  to  draw-bar  stress  to  be  applied  to  cover  loss  in  trans- 
mission from  cylinder  to  draw-bar  are  as  follows  : 


(44) 


(45) 
..     .     (46) 

Draw-bar  stress  corrected  for  the  several  losses  is  as  follows: 

Ti-f-f,-  161—3.8^  ........     (48) 


(49) 


2.  .     .     .     (50) 


In  these  equations  the  characters  employed  signify  as  follows: 

I.  H.  P.  =  indicated  horse-power; 

C.H.  P.  =  cylinder  horse-power,  not  necessarily  obtained  by  means  of 
an  indicator,  but  estimated  to  be  equivalent  to  power  thus 
obtained; 

f/  =  square  feet  of  heating-surface  in  boiler; 
V  =  speed  in  miles  per  hour; 
PF  =  tons  weight  of    rolling  load,  including  that  on  trucks  and 

tender,  but  excluding  that  on  drivers; 
w=tons  weight  carried  by  drivers; 
d=  diameter  of  piston  in  inches; 
L  =  length  of  stroke  in  feet; 
D  =  diameter  of  drivers  in  feet; 

f  =  tractive  force  in  pounds  equivalent  to  the  power  developed 
in  the  cvlinders,  assuming  no  loss  in  transmission: 


GENERALIZATION.  425 

t\=  tractive  force  in  pounds  equivalent  to  the  machine  friction, 

including  the  rolling  friction  of  drivers ; 

t2=  tractive  force  in  pounds  equivalent  to  the  resistance  of  the 
rolling  load,  including  that  of  trucks  and  tender,  but  ex- 
cluding that  of  drivers; 

*3=  tractive  force  in  pounds  equivalent  to  the  resistance  offered 
by  still  air  to  the  movement  of  an  engine  at  the  head  of  a 
train,  bein^  the  same  factor  which  is  defined  as  A  in  sec- 
tion (6)  of  paragraph  211. 

TI=  tractive  force  in  pounds  equivalent  to  cylinder  power  cor- 
rected for  machine  friction.  The  application  of  the  equa- 
tion for  t\  to  the  New  York  Central  engine  gives  the  line 
CD,  Fig.  228; 

T2=  tractive  force  in  pounds  equivalent  to  cylinder  power  cor- 
rected for  machine  friction  and  resistance  of  rolling  load. 
The  application  of  this  equation  for  T2  to  the  New  York 
Central  engine  gives  the  line  EF,  Fig.  228; 

TS=  tractive  force  in  pounds  equivalent  to  cylinder  power  cor- 
rected for  all  losses  between  cylinders  and  draw-bar,  in- 
cluding machine  friction,  resistance  of  rolling  load,  and 
atmospheric  resistance.  The  application  of  the  equation 
for  T3  to  the  New  York  Central  engine  gives  the  line  GH, 
Fig.  228;  T3  must  never  be  greater  than  1/4w. 

By  solving  for  7"3,  the  net  draw-bar  stress  for  any  locomotive,  at 
any  speed,  may  be  found.  The  facts  which  are  required  to  be  known 
are,  area  of  heating-surface,  diameter  and  stroke  of  pistons,  diameter 
of  drivers,  the  weight  of  the  rolling  load,  and  the  weight  on  drivers. 
No  value  for  T3  thus  obtained  should  be  considered  practicable  if 
greater  than  one-fourth  the  weight  on  drivers. 


f    UH1VERSITY   1 

'-,    ,      ItvSS 


INDEX. 


A  PAGE 

Actual  evaporation 127 

<<              "         ,  table  giving 128 

' '      trains,  atmospheric  resistance  to 399 

Air-supply  for  atmospheric  resistance  tests 378 

Alden  friction  brakes,  the 13 

"           "           "      ,  drawing  of  the 14 

Allen  link,  drawing  of 317 

Ash-pan,  refuse  caught  in 181 

' '       ,  table  showing  refuse  caught  in 182 

Atmospheric  resistance  to  the  motion  of  railway  trains 377 

"                     "       ,  plan  of  experiments  concerning 378 

11                    "       ,  conclusions  concerning 406 

Axles,  the  supporting 12 

' '     ,  drawing  of  the  supporting 13 

B 

Back  pressure,  chart  showing 140 

Balancing,  the  problem  of 321 

Blower,  the  Sturtevant 11 

' '       for  waste  gases,  illustration  of 12 

Bio  wing -thro  ugh  effect,  the 303 

Boiler,  the 125 

' '     ,  dimensions  of 52 

"     ,  performance  of 115,  411 

' '     ,  effect  of  thick  firing  upon  performance  of 167 

* '     ,  table  showing  performance  of 86 

"     ,  power  of 132 

* '     ,  efficiency  of 156 

* '     ,  thermal  efficiency  of 137 

"     ,  drawing  of '. 56,  189 

* '     ,  chart  showing  pressure  of ' 127 

* '     ,  conclusions  with  reference  to  performance  of 153 

427 


428  INDEX. 

PAGE 

Brakes,  the  Alden  friction 13 

' '      ,  drawing  of  tne  Alden  friction 14 

' '      ,  work  absorbe    by 21 

"      ,     "     performed  by 21 

Branch-pipe,  drawing  of 54 

Buckeye  engine,  arrangement  of  pipes  and  indicators  on 272 

C 

Capacity,  pressure  vs 367 

Carnegie  Institution,  tests  under  the  patronage  of  the 371 

Choice  of  a  locomotive,  conditions  controlling 46 

Clearance  as  affected  by  different  lengths  of  indicator-pipes 276 

1 '          "  affecting  events  of  stroke,  inside 301 

"          "         "         indicator-cards,  inside 301 

tl          il         "         steam  consumption,  increased 306 

1 '        ,  diagram  showing  steam  consumption  and  inside 30 

1 '        ,  excessive 304 

,  range  of 309 

Coal,  analysis  of. 82 

' '    ,  composition  of 132 

"    ,  kind  of 82 

' '      and  combustible 132 

' '    ,  consumption  of 134,  141 

' '   per  I.H.P.  per  hour,  diagram  showing 119 

"     "    D.H.P.  •"     "    ,  •      "              "         120 

"     "    mile  run,  diagram  showing 122 

Coefficient  of  friction,  definition  of  apparent 16 

Combustible,  coal  and 132 

,  rate  of 137,  138 

Combustion  and  coal,  table  showing 134 

' '          ,  high  rates  of. 156 

' '          ,  losses  due  to  incomplete 163 

Computation,  methods  of 76 

Conduit  used  in  experiments  concerning  atmospheric  resistance 378 

' '       employed  in  atmospheric  resistance  tests,  view  within  the 386 

Constants  for  locomotive 49 

Counterbalance,  weights  of 327 

' '              ,  action  of  the 321 

' '              ,  conclusions  concerning 331 

Course  followed  by  locomotive,  drawing  showing 4 

Cover,  drawing  of  the  valve-box  and 58 

Coverings,  tests  of  boiler. 193 

".'"..'*,  efficiency  of  boiler 203 

Critical  speed,  definition  of 112 

Cross-head,  drawing  of 60 

Cut-off  as  affecting  form  of  indicator-cards,  speed  and 103 

«      "        ««        mean  effective  pressure,  speed  and 106 


INDEX.  429 

PAGE 

Cylinder  and  saddle,  drawing  of 57 

' '  condensation 112 

1 '  diagrams,  form  of 276 

' '  and  draw-bar,  losses  between 417 

1  {  performance 413 

' '  heads,  drawing  of 59 

Cylinders,  table  showing  thermal  action  within 115 

D 

Data  covering  forty-four  efficiency  tests 71 

"    ,  selection  of 124 

' '    ,  application  of 411 

' '    ,  observed  and  calculated 160 

Deflector-plate,  drawing  of  netting  and 55 

Departure  of  Schenectady  No.  1,  photograpn  showing 39 

Derived  relations 150 

Dimensions  of  locomotive,  summary  of 50 

"           ''boiler 52 

"           "  stacks,  drawings  showing 229 

"           "  nozzles,  drawing        "       229 

Distribution  of  draft 209 

"            "     "    ,  diagram  showing 210 

Draft 137 

' '    ,  table  showing 138 

"    ,  chart        "       139 

"    ,  distribution  of 209 

1 '    ,  diagram  showing  distribution  of 210 

"    ,  table  showing  percentage  of 211 

' '    ,  diagrams  showing  values  of 237 

1 '    ,  table  giving  changes  in 239 

' '    ,  unavoidable  loss  in 251 

Draw-bar,  performance  at  the 118 

11       ,  diagram  showing  pull  at  the 120 

' '       ,  difficulties  encountered  in  measuring  stresses  at  the 334 

"      pull 414 

' '       ,  losses  between  cylinder  and 417 

' '       stress,  equations  for , 423 

Drawings  of  locomotive 49 

Driving-wheels,  diameter  of 373 

Dry-pipe,  drawing  of 54 

Dynamometer,  the  traction 18 

' '            ,  drawing  of  the  locomotive 19 

' '            ,  illustration  of  the 22 

"            ,  the  Emery 27 

"            horse-power,  drawing  showing 121 

"            car,  drawing  of  model '...... 383 


430  INDEX. 


E 

PAGE 

Eccentric  strap,  drawing  of W4 

rod,  drawing  of 64 

' '        ,  drawing  of 65 

Efficiency  of  boiler,  power  and 148 

of  the  boiler,  thermal 137 

as  affected  by  quality  of  fuel i  13 

"         ,  diagram  showing  rate  of  evaporation  and 144 

Emery  dynamometer,  the 27 

Engineering  laboratories  at  Purdue,  growth  of 1 

' '            laboratory,  1891,  illustration  of  the 5 

' '         ,  ground  plan  of 5 

"        prior  to  January,  1894,  illustration  of 24 

"                    "         ,  burning  of 24 

"                    "         ,  plan  of  the  reconstructed 38 

Engine,  experiments  upon  a  stationary 270 

{ '       performance,  table  showing 90 

Equivalent  evaporation,  quality  of  steam  and 129 

per  hour,  diagram  showing 116 

"                    "          ,  table  showing 130 

Evaporation,  actual 127 

,  diagram  showing  rate  of 144 

,  equivalent 129 

,  table  giving  actual 128 

,  table  giving  equivalent 130 

Evaporative  efficiency,  diagram  showing 117 

performance  as  affected  by  increased  power 142 

"                      "        ,  table  giving 14? 

Events  of  stroke 105 

.  "       "      "    ,  table  showing 106 

"       "      "      as  affected  by  lead 283 

"       "      "       "        "        "  inside  clearance 301 

Excess  air,  losses  due  to 163 

Excessive  clearance 304 

Exhaust,  character  of 145 

"          fan,  the 23 

' '         pipe  and  nozzle,  drawing  of 53,  230 

"          J3t,  action  of 212 

"           "  ,  illustration  of  apparatus  used  in  exploring 213 

"         nozzles 227 

"              ' '      ,  drawing  showing  dimensions  of 229 

' '          nozzle  as  affecting  stack,  changes  in 247 

Experimental  train,  illustration  of  head  of 187 

' '             boiler  and  its  equipment,  the 188 

"     ,  drawing  of. 189 


INDEX.  431 


Feed-water  log 71 

Fire,  condition  of • 167 

Fire-box,  drawing  of 228 

Fireman,  influence  of 171 

First  model  of  a  train,  forces  to  be  resisted  by 394 

First  plant,  behavior  of  mounting  mechanism  of 20 

' '        "     ,  work  of  the 24 

Forces  acting  throughout  the  length  of  a  model  train,  distribution  of 395 

Forces  and  velocity  of  current  acting  upon  models  of  a  train,  relation  of 

resulting 396 

Freight-cars,  atmospheric  resistance  offered  to  trains  of 404 

Frict^n-brakes,  the .^ 7 

,  the  Alden * 13 

'  '  ,  drawing  of  the 14 

' '  ,  illustration  of 16 

Friction  horse-power,  diagram  showing 121 

' '        tests,  results  of 347 

Front  end,  the 209 

"        "  ,  committee  on .- 226 

"        <f  ,  definition  of  the ( .209 

"        "  ,  plan  of  tests  of 226 

"        "  ,  results  of  tests  of 231 

"        "  ,  summary  of  results  of  tests  of 255 

' '        "  ,  review  of  best  results  of  tests  of 240 

"        "  ,  later  experiments  concerning  the 257 

"        "  ,  drawings  showing  best  arrangement  of 259 

"        "  ,  standard 261 

Fuel-log 72 

Fuel,  quality  of 148 

G 

General  conditions  employed  in  testing,  table  showing 83 

* c                ' '         with  reference  to  boiler  performance 125 

"      "    tests,  table  showing 126 

Guides,  drawing  of 61 

Guide-yokes,  drawing  of 61 

Grate,  forms  of 158 

' '    ,  losses  at , 159 

>,       "     ,  conditions  at  the 227 

' '      losses  as  affected  by  spark  losses 159 

H 

Heat  radiated  from  a  locomotive  boiler 185 

Heat  radiated,  amount  of .   185 


432  INDEX. 

PAGE 

Heating  surface,  definition  of 65 

"             "      ,  losses  along 163 

' f        value  of  sparks,  the 178 

"      "       "     ,  diagram  showing 179 

High  steam-pressures,  thermal  advantages  of 364 

Higher  pressures,  arguments  concerning 365 

Horse-power,  indicated 107 

' '         ,  diagram  showing  dynamometer 121 

"         ,        "            "        friction 121 


I 

Increased  clearance  as  affecting  steam  consumption 306 

Indicator  record ,, . . .  74 

"         cards 354 

"            "as  affected  by  changes  in  speed  and  cut-off,  form  of 103 

"            "    ,  diagram  showing  effect  of  speed  and  cut-off  on  form  of. ...  104 

•'            "    ,  effect  of  lead  upon 287 

"            "as  affected  by  changes  in  lap 293 

"            "      "        "        "  inside  clearance 301 

Indicated  horse-power 107 

"                  ' '          ,  diagram  showing 109 

Indicator  rigging,  drawing  of 268 

Indicator  work,  conclusions  with  reference  to 281 

Indicators  on  Buckeye  engine,  arrangement  of 272 

Influence  of  the  fireman 171 

Inside  clearance,  effect  of 298 

"            tl          as  affecting  indicator-cards 301 

"            "           "        "        events  of  stroke 301 

"             ' '          and  steam  consumption,  diagram  showing 308 

Items  appearing  in  tables,  definition  of 76 


* 

Jet,  form  and  character  of  exhaust 218 

Jet  as  affected  by  changes  in  speed,  the 219 

»"        "         "        "•       "bridge,the 220 

"    "        "         "   cut-off,  the 225 

"    "        <'        "  stack,  the 224 

"    "        "        "  bars  over  the  tip,  the 223 

"    "  influenced  by  tips,  the 222 

'*   formed  by  a  steady  blast  of  steam 221 

' '  ,  drawing  showing 219 

«,       "  "        form  of 216 

Joy  gear,  the 317 

"   '/  ,  drawing  of  the 318 


INDEX.  433 


Laboratory,  1891,  illustration  of  the  engineering 5 

' '         ,  1894,  drawing  of  the  engineering 5 

' '         ,  ground  plan  of  the  engineering 5 

' '        prior  to  January,  1894,  illustration  of 24 

' '         ,  burning  of  engineering 24 

' '         ,  plan  of  the  reconstructed  engineering 38 

Laboratories  at  Purdue,  growth  of  engineering 1 

Lap,  definition  of  outside 291 

"'        '"  steam.  .  .  " 291 

Last  model  of  a  train,  atmospheric  forces  to  be  resisted  by 395 

Lead,  definition  of 282 

' '    ,  determination  of 282 

' '    ,  tests  involving  different  amounts  of 283 

"    ,  effect  of 282 

' '       as  affecting  indicator-cards 287 

11     "        "        valve-travel  and  port-opening 285 

' '     and  machine  friction 290 

' '    ,  conclusions  concerning 290 

Links,  drawing  of 63 

Link,         "   .    "  Allen 317 

",         "       "stationary 317 

Link-block,  drawing  of 63 

Locomotive,  choice  of 46 

"          ,  arrival  of  first 2 

1 '          ,  course  followed  by  first 4 

"          in  the  laboratory,  illustration  of  the 6 

' '          ,  elevation  of  mounting  of 8 

"          ,  plan  of  mounting  of 10 

' '          dynamometer,  drawing  of  the 19 

"          ,  sale  of  the 39 

' '          ,  specifications  for  the 49 

' '          ,  arrival  of  second 41 

' '          ,  constants  for 49 

"          ,  dimensions  of 50 

' '          ,  drawings  of 49 

"          ,  balancing  of 325 

"          ,  power  of 227 

"          ,  reciprocating  parts  of  a 322 

"           and  tender,  resistance  offered  to 4C3 

"          ,  application  of  deduced  results  to  a  typical 421 

"           kboratory  1894,  drawing  of  the 37 

"                  "            "   ;  illustration  of  the 38 

"           operation.  . 42 

under  conditions  other  than  those  of  the  track 42 

"           performance ' 99,  117 


434  IXDEX. 

PAGE! 

Locomotive  performance,  generalization  concerning 411 

' '           ,  results  concerning 423 

,  illustration  of  the  second 40 

testing-plant,  considerations  leading  to 1 

"                                 ,  establishment  of 1 

"  "  ,  growth  of  interest  in 43,  44 

"                  "            after  the  fire,  illustration  of  the 25 

"                  "            ,  the  second 25 

' '          valve-gears 310 

Losses  along  the  heating-surface 163 

' '      due  to  incomplete  combustion 162 

"       by  radiation. .  .  _ 185 

M 

Machine  friction 333 

"      ,  lead  and 290 

"             ' '      ,  conclusions  concerning 349 

Maximum  power  dependent  upon  efficiency 119 

Mean  effective  pressure  as  affected  by  inside  clearance 305 

"  speed  and  cut-off 106 

1 '       ,  diagram  showing 108 

Miller,  extract  from  letter  of  Robert 41 

Model  dynamometer  car,  drawing  of 383 

'  *      cars  employed  in  tests  to  determine  atmospheric  resistance 382 

"      of  a  train,  forces  acting  upon  the  first 394 

"      "  "     "    ,  forces  acting  upon  the  second 395 

"       "  "    "    ,  forces  acting  upon  the  last 395 

"      train,  distribution  of  forces  acting  throughout  the  length  of  a 395 

Models  between  the  second  and  last  car  of  a  train,  forces  acting  upon 395 

"      ,  forces  acting  upon  trains  of  three,  five,  ten,  and  twenty-five 394 

Mounting,  plan  of  locomotive 6 

' '        ,  elevation  of  locomotive 8 

' '         mechanism,  behavior  of  the 20 

N 

Netting  and  deflector-plate,  drawing  of 55 

New  plant,  work  with  the 34 

' '     testing-plants 45 

' '     wheel  foundation,  the 25 

Nozzles,  experimental 228 

O 

Observers  employed  in  testing  69 

Oil  circulation,  drawing  of  the  arrangement  for 15 

Outside  lap,  definition  of 291 

"         '  •'    as  affecting  indicator-cards 293 


INDEX.  435 


Passenger-cars,  atmospheric  resistance  offered  to  trains  of. 404 

Pipe,  differe.it  lengths  of  indicator 273 

Piston,  drawing  of 60 

Piston-rod,  drawing  of 60 

Pitot  tube,  drawing  of 379 

Port-opening,  effect  of  lead  upon 285 

' '           ,  determination  of 286 

Power  and  efficiency  of  boiler. . . .  ., 148 

"      of  boiler 132 

"      variation 296 

1 '      developed  by  boiler,  table  showing 133 

Pressure  vs.  capacity 367 

Pressure  as  affected  by  inside  clearance,  mean  effective 305 

"•        as  affected  by  speed  and  cut-off,  mean  effective 106 

tl        on  bra  es,  photograph  showing  mechanism  for  controlling 22 

Pressures,  tests  at  different 366 

Pull  at  draw-bar,  diagram  showing 120 

Purdue  University,  opening  of 1 

' '      ,  interest  in  the  work  of 44 

Q 

Quality  of  fuel  as  affecting  efficiency 148 

"        "  steam 129 

"        "      "     ,  table  showing 130 

R 

Radiation 204 

' '         loss,  diagram  showing  effect  of  speed  on 206 

"         losses 185 

"      upon  the  road 186 

' '     ,  coal  required  to  maintain 205 

' '        ,  table  showing  power  lost  by 205 

' '         ,  conclusions  concerning  loss  by 208 

Reciprocating  parts  of  a  locomotive 322 

Reconstructed  laboratory,  plan  of  the 38 

Refuse  caught  in  ash-pan 181 

"      ,  table  showing 182 

Results  of  thirty-five  efficiency  tests 168 

"      ,  interpretation  of 169 

Revolution  counters,  illustration  showing 22 

Reverse-lever,  drawing  of 66 

' '      -shaft,  drawing  of 65 

Rocker,  drawing  of 63 


436  INDEX. 

PAGE 

Running  log 70 

"     tests 196 

"          "  ,  table  giving  results  of 197 

.    S 

Saddle,  drawing  of  cylinder  and 57 

Second  locomotive,  illustration  of 40 

Second  model  of  a  train,  forces  acting  upon  the 395 

Second  testing-plant,  the 25 

* '                   "         ,  elevation  of 26 

.  "         ,  floor  plan  of 33 

"                  "         ,  interior  view  of  the 35 

"                  "         ,  plan  of  the 28 

"                  "         ,  section  of 32 

Schenectady  No.  1,  specifications  for .- .  47 

"                ",  arrival  of 2 

"                "  ,  elevation  of 46 

' '                "  in  a  new  role,  illustration  showing 39 

"    .  "   ,  illustration  of 3,  40 

' '                "  ,  illustration  showing  the  departure  of 39 

"                "  ,  sale  of 39 

Setting  of  valves  of  Schenectady  No.  1 52 

"      "       "      in  connection  with  tests  to  define  cylinder  performance.  .  .  103 

Smoke-box,  superheating  in  the 262 

' '       ,  temperature  of 137 

' '       ,  table  giving  temperature  of 138 

Sparks 173 

Spark  discharge,  drawing  showing  density  of 183 

Sparks,  heating  value  of 178 

' '      ,  diagram  showing  heating  value  of 179 

"      ,  losses  of 173 

' '       passing  out  of  stack,  drawings  showing 183 

"      ,  sample  of 184 

"      .  size  of 183 

' '      ,  volume  of 179 

Spark  losses  as  affecting  grate  losses 159 

"         ' (     ,  diagram  showing 177 

"     ,  table  showing 180 

"      trap,  the 174 

"   ,  diagram  of 174 

Specifications  for  locomotive 47 

Speed  and  cut-off  as  affecting  form  of  indicator-cards 103 

"     "          "      mean  effective  pressure 106 

Stack,  problem  of 225 

"     ,  plan  of 175 

' '     ,  form  of ,_ 226 


INDEX.  437 


Stack,  diameter  of 226 

' '     ,  height  of 227 

' '     ,  relation  of  height  to  diameter  of 243 

' '     ,  effect  of  different  proportions  of 237 

1 '     ,  equations  giving  diameter  of 248 

' '      as  affected  by  changes  in  exhaust-nozzle 247 

Stacks,  experimental 228 

.    "      ,  drawings  showing  dimensions  of 229 

' '      ,  straight 244 

' '      ,  equations  for  straight 244 

' '      ,  tapered 246 

' '      ,  equations  for  tapered 247 

' '      ,  relative  advantage  of  straight  and  tapered 254 

Standing  tests  to  determine  radiation  losses 194 

' '  "    ,  table  showing  results  of 195 

Stationary  engine,  experiments  involving  different  lengths  of  indicator-pipes 

upon  a 270 

' '          link,  drawing  of 317 

Steam,  consumption  of 110 

' '     ,  dryness  of 131 

"      accounted  for  by  indicator,  percentage  of 113 

' '     ,  quality  of 129 

' '     ,  table  showing  quality  of 73,  130 

' '      accounted  for  by  indicator  at  cut-off,  percentage  of 114 

' '      consumption  as  affected  by  lead 289 

"  "  "       "         "  outside  lap 296 

' '  increased  clearance 306 

"       "         "  throttling 360 

' '  ,  table  showing 290 

,  diagram  showing  inside  clearance  and 308 

' '       engine  indicators 269 

' '      lap,  definition  of 291 

' '      passages,  areas  of 53 

' '       passage  areas,  diagram  showing 68 

' '       port,  maximum  opening  of 300 

' '       pressure,  table  showing  drop  in 107 

Stephenson  valve-gear 310 

gear  does,  what  the 311 

Straight  stacks 244 

{ '     ,  drawing  showing  proportions  for.  . 251 

' '        and  tapered  stacks,  relative  advantage  of 254 

Summary-sheet 75 

Superheating  in  the  smoke-box 262 

Superstructure,  the 31 

Supporting  axles,  drawing  of  the 13 

' '  wheels,  the 7 

"  "    ,  movement  of  the 9 


438  INDEX. 

T 

PAGE 

Tapered  stacks.  . 246 

' '            ' '     ,  drawing  showing  proportions  for 250 

"            "     ,  relative  advantag3  of  straight  and  tapered 254 

Tender,  resistance  offere    by  atmosphere  t    locomotive  and 403 

Testing  plant,  consid:  rations  leading  to  design  of 1 

"          ' '    -,  elevation  of  the  second 26 

' '           ' '     ,  establishment  of  locomotive 1 

"          "     ,  the  first 4 

"     ,  work  of  the  first 24 

"          "      immediately  after  the  fire,  illustration  of 25 

"          "     ,  the  second . ' 25 

"          "    ,  plan  of  the  second 28 

"          "    ,  sectiDn  of  the  second 32 

tl          "     ,  floor  plan  of  second 33 

' '       plants,  new 45 

' '      ,  observers  employed  in 69 

"      ,  method  of 69 

Tests,  the 102 

' '     ,  conditions  of  the. 175 

"    ,  outline  of 168 

"      to  determine  heat  losses  by  radiation  upon  the  road,  plan  of 187 

"     ,  movements  during  the  radiation 191 

1 '      of  coverings 194 

"     ,  front-end 231 

' '      involving  different  amounts  of  lead 283 

"     ,  results  of 168 

Thermal  units,  performance  in  terms  of 135 

11    ,  table  sho'wing 13G 

' '        efficiency  of  the  boiler 137 

Thermometer-cup,  drawing  of 264 

Three,  five,  ten,  and  twenty-five  models  in  experiments  upon  atmospheric 

resistance 394 

Throttle,  drawing  of 67 

' '          lever,  drawing  of 66 

' '          pipe,  drawing  of 67 

Throttling  as  affecting  steam  consumption 360 

,  effect  of 353 

tests 353 

Track,  the 190 

Train,  illustration  of  head  of  experimental 187 

' '     ,  resistance  offered  to  any 405 

Two  models  in  experiments  upon  atmospheric  resistance 394 

V 

Valve,  acceleration  of  the 311 

' '      box  and  cover,  drawing  of & 


INDEX.  439 

PAGE 

Valve  diagrams ; . 292 

"      ellipse 311 

* '     ,  drawing  of 62 

' '      gear,  a  Stephenson 310 

"        "     design  as  affected  by  wire-drawing 312 

' '      gears,  adaptability  of 319 

"         "    ,  determination  of  lead  for 282 

' '         "    ,  improved 314 

"         "    ,  locomotive 310 

* '         "    ,  conclusions  concerning 320 

4 '      motion  diagram 312 

* '      travel,  device  for  measuring ,. 286 

"          "     ,  effect  of  lead  upon 285 

' '      rod,  drawing  of  steam-chest 62 

' '      yoke,  drawing  of '. 62 

Valves,  proportions  of 52 

"     ,  the  setting  of 103 

' '     ,  table  showing  setting  of 52 

Velocity,  relation  of  force  and 396 

Volume  of  sparks 179 

von  Borries-Troske  tests,  the 225 

W 

Walschaert  gear,  the 318 

"  "  ,  drawing  of  the 318 

Water,  diagram  showing  evaporation  of 142 

Weight  of  sparks  passing  from  the  stack 176 

Wheel  diameters,  practice  concerning 373 

' '  foundation,  the  new 25 

Wire-drawing 106 

as  affecting  valve-gear  design 312 

Work  absorbed  by  brakes! 21 

"      with  the  new  plant ' 34 


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LD  21-95t»-7,'37| 


